Caves & Cliffs



Caves & Cliffs is the name of one released and one upcoming major themed update set to release only for the of Minecraft. The first part was released as Java Edition 1.17 and Bedrock Edition 1.17.0 on June 8, 2021, which added geodes, copper, and new blocks and mobs. The second part will be released as Java Edition 1.18 and Bedrock Edition 1.18.0 at the end of 2021 and will include expanded caves, increased height and depth limit, new mountain generation, and new biomes. It was announced in Minecraft Live 2020, and on April 14, 2021, Mojang Studios announced that the update would be split into two updates due to the amount and complexity of content, as well as team health.

This update's development on started with snapshot 20w45a, which was released on November 4, 2020. The first pre-release for Caves & Cliffs: Part I was released on May 27, 2021, and the first release candidate on June 4, 2021.

This update's development on started with beta 1.16.200.52, which was released on October 28, 2020. Most of the Part I features were behind experimental gameplay toggle until the Part I release and were not included in the full 1.16.200, 1.16.210, and 1.16.220 release.

Both Java and Bedrock received Caves & Cliffs: Part I on June 8, 2021.

Blocks

 * Amethyst Buds and Amethyst Cluster
 * Grow on any side of budding amethyst blocks over time.
 * Emit a small amount of light.
 * Can be placed on any solid block in any direction, regardless of on land or in water.
 * Require at least an iron pickaxe to mine, otherwise drops nothing.
 * Breaking a fully developed amethyst cluster with a non-Silk Touch pickaxe drops 4 amethyst shards.
 * These can be crafted into spyglasses and tinted glass.
 * Using Silk Touch on an amethyst bud or cluster drops the block as an item.


 * Azalea
 * Has variants of bushes and trees with either no blossoms or pink blossoms called flowering azalea.
 * Can be found in the lush caves biome.
 * Can be obtained from azalea leaves.


 * Azalea Leaves


 * Part of a new tree (azalea tree), marking the location of a lush cave.
 * Has variants with either no blossoms or pink blossoms called flowering azalea leaves.
 * Drop azaleas when broken, similarly to other leaf blocks dropping saplings.


 * Big Dripleaf


 * A plant that can be used for platforming.
 * If a player or mob stands on top of the plant for two seconds (40 ticks), the plant tilts and the player or mob falls through the plant.
 * Tilts even if the player is sneaking.
 * Also tilts if hit by a projectile (such as snowballs, arrows, etc.).
 * Does not tilt when powered by a redstone block, unless hit by a projectile.
 * Can be placed on any solid block and water.
 * Can have bone meal applied to grow taller.
 * Can be used for new projects and obstacle courses.


 * Block of Amethyst


 * Can be crafted with four amethyst shards.
 * Naturally generates in amethyst geode structures.
 * Makes a sparkling sound when placed or walked on.


 * Budding Amethyst


 * When it receives a random tick, it has a 20% chance to generate or grow an amethyst bud on one of its sides.
 * Relatively rare, generates only in amethyst geode structures.
 * Only obtainable in Creative Mode.


 * Calcite


 * Spawns between smooth basalt and blocks of amethyst, much like real-life geodes.
 * Visually similar to diorite, but with a smoother texture.
 * Found underground surrounding the outsides of amethyst geode formations.


 * Candles and Candle Cakes


 * A light source with a light level of 3.
 * Up to four can be placed in a single block, similar to sea pickles. If 1 more candle is placed in a block, it increases the light level by 3, making a max light level of 12.
 * Can be placed in water, but cannot be lit when waterlogged.
 * Can be lit with a flint and steel, fire charge, an arrow fired from a flame-enchanted bow, or a fire charge shot by a dispenser if it hits the candle.
 * Emits fire particles when lit.
 * The player can left-click it to snuff it.
 * Can be placed only if there is a solid surface below.
 * Can still float if the block below them is broken.
 * Have variants for uncolored and all 16 colors.
 * Uncolored candle is crafted with 1 string and 1 honeycomb.
 * Colored candle is crafted using one of the 16 dyes and one uncolored candle.
 * Right-clicking a candle on an uneaten cake makes a "birthday cake", which can have 1 candle placed on it.
 * If the cake is eaten, the candle pops off.
 * Lit candles have a different texture than unlit candles.


 * Cauldron


 * Can now be filled with lava $$, which was previously a exclusive.
 * Striders are not affected by lava cauldrons.
 * Can now be filled from the snowfall in mountains creating powder snow, which can be collected using buckets.


 * Cave Vines


 * Grow on the bottom side of a block.
 * Grow in Lush Caves.
 * Can be planted using glow berries.
 * Produce edible glow berries, which are a light source.
 * Glow berries on the body of the plant produce a higher light level compared to the tip (bottom-most) of the plant.
 * Using bone meal on a cave vine produces glow berries (similar to sweet berry bushes) instead of growing the vine itself, unlike other vines.
 * Can be extended downward using glow berries, and has an age mechanic, similar to kelp, such that every time it ages it has a chance to grow Glow Berries.


 * Cobbled Deepslate


 * Takes slightly longer to mine than normal stone.
 * Mining deepslate without Silk Touch drops cobbled deepslate, similar to stone dropping cobblestone.
 * Can be crafted or cut into the following blocks:
 * Deepslate Slab
 * Deepslate Stairs
 * Deepslate Wall
 * Polished Deepslate
 * Polished Deepslate Slab
 * Polished Deepslate Stairs
 * Polished Deepslate Wall
 * Deepslate Bricks
 * Deepslate Brick Slab
 * Deepslate Brick Stairs
 * Deepslate Brick Wall
 * Deepslate Tiles
 * Deepslate Tile Slab
 * Deepslate Tile Stairs
 * Deepslate Tile Wall
 * Chiseled Deepslate


 * Copper Block and variants


 * Copper blocks are used for crafting and storage.
 * Made with nine copper ingots.
 * The stonecutter can be used to craft the different copper block variants.
 * Only cut copper can be used to make stairs and slabs.
 * Made with four copper blocks.
 * Cannot be turned back into regular copper blocks or copper ingots.
 * Develops a patina of pale green copper carbonate over multiple stages,(exposed weathered, and oxidised), which might be sped up by weather such as rain.
 * Honeycombs can be used to make waxed copper, which does not progress beyond the patina stage it has at the time. The wax can be scraped off with an axe, but it does not drop the honeycomb.
 * Axes can be used to undo the oxidisation stages one at a time.
 * Drowned can drop copper ingots.


 * Copper Ore


 * New ore that is found underground.
 * Drops Raw Copper when broken, like other metal ores.
 * Spawns in ore veins similar to iron (current generation is not the final version).
 * Can be smelted into a copper ingot, which can be used to craft copper blocks, lightning rods, and spyglasses.
 * Does not generate below Y = 0.


 * Deepslate


 * Can be found below Y = 0.
 * Generates as base stone below Y = 0, gradually replacing stone.
 * Previously known as "grimstone".
 * Has similar texture to cobbled deepslate but with a different top texture.
 * Is slightly tougher to mine than normal stone.
 * Drops cobbled deepslate when mined without the Silk Touch enchantment.
 * Is rotated when placed depending on the players orientation.


 * Deepslate Ores


 * New overworld ore variants that generate in the deepslate layer (below Y = 0).
 * Functionally similar to their normal ore variants but take twice as long to mine.
 * Ores that generate with deepslate variants include iron, gold, lapis lazuli, diamond, and redstone.
 * Ores that do not generate below Y = 0 still have deepslate variants, however these variants do not generate naturally.


 * Dripstone Block


 * Spawn in Dripstone Caves.
 * Can be used to grow Pointed Dripstone.
 * Can be crafted from four pointed dripstone.


 * Glow Lichen


 * A decorative block.
 * Can be waterlogged.
 * Looks similar to vines.
 * Emits a light level of 7.
 * Spreads to a random nearby block in a cross formation when bone meal is applied.
 * Generates in caves.
 * This block was hinted at by Henrik Kniberg, who explained that the glowing ores at Minecraft Live 2020 were prototypes for this.


 * Hanging Roots


 * Seen in the distance of a lush caves biome behind a spore blossom.
 * A decorative block.
 * Bonemealing rooted dirt causes it to grow on the bottom of the block. ausescthis to grow on the bottom block.


 * Lightning Rod


 * Crafted with 3 copper ingots.
 * Redirects nearby lightning strikes to the top of the rod, which can prevent flammable structures from catching fire during thunderstorms.
 * Emits a redstone signal when struck by lightning, with the exception of when it gets struck by lightning from a channeling trident in a thunderstorm, in which it emits nothing.
 * Can be oriented in different directions depending on the players orientation.


 * Raw ore Blocks


 * Crafted from 9 Raw Iron, Raw Gold or Raw Copper.


 * Moss Block


 * An opaque block that appears grassy on all sides.
 * Using bone meal can cause it to grow grass, tall grass, moss carpet s and both types of azalea bushes on it and in its vicinity.
 * Bone meal can also cause it to grow over (expand) and convert stone surfaces, sand, dirt, etc. but not grass surfaces.
 * Breaks when pushed by a piston.


 * Moss Carpet


 * Same texture as the moss block, but one pixel thick like carpet.
 * Can occupy the same block with grass.


 * Pointed Dripstone


 * Comes in two forms, stalactites and stalagmites.
 * Stalactites hang from the ceiling and drip water or lava, based on what is above them. The stalactites drip water naturally without a source block above it, but these drips do not fill a cauldron.
 * Placing a cauldron under a stalactite slowly fills the cauldron with water or lava depending on the source block above them (enables renewable lava).
 * If the block on which a stalactite hangs is broken, the stalactite falls, causing damage to players and mobs directly underneath. They do not take any damage if they are airborne.
 * Stalagmites are found on the floor of the cave and deal damage if landed on.
 * The damage inflicted of pointed dripstone is directly proportional to the height from which the stalactite or player/mob falls from.
 * If a stalactite and stalagmite of any two lengths are placed directly above and below each other, they conjoin into a column. If one is placed while the player is crouching, they stay separate.


 * Powder Snow


 * Similar to snow, but entities fall through it. The fall is similar to the effect of cobwebs, but faster.
 * If the player does not have any leather armor equipped and they walk or fall in, they start to freeze and take damage.
 * Freezing lowers the player's FOV (field of view), turns the health bar blue, and puts a frosty vignette on their screen.
 * Any leather armor prevents freezing.
 * Wearing leather boots allows the player to walk on top of powder snow and make it function like scaffolding.
 * Most mobs can also take freezing damage. Polar bears, strays, and snow golems are immune to freezing.
 * Certain mobs have unique properties with powder snow.
 * Skeletons convert into strays after staying inside of powder snow for too long.
 * Goats avoid and jump across powder snow.
 * Foxes, rabbits, endermites, and silverfish can walk on top of powder snow.
 * Shulkers and vexes are unaffected by powder snow.
 * "Snowier snow" was announced to be part of the Mountains biome in the biome vote at MINECON Live 2019, a joke teaser for powder snow.
 * Cauldrons slowly fill up with powder snow when they are placed in a snowing.biome


 * Rooted Dirt


 * Part of the Azalea plant.
 * Resembles a dirt block, but with the roots of the Azalea tree intertwined.
 * The first roots that exist in Minecraft.
 * Planned to lead to the Lush Caves biome.
 * When bonemealed, hanging roots grow on the bottom block.


 * Sculk Sensor


 * Generates in the deep dark cave biome.
 * Can be used for wireless redstone.
 * Senses vibrations created by things such as block placement, footsteps, entities such as cows or zombies, and projectiles, including fishing rods.
 * Wool can occlude its ability to sense in a certain direction. This can be placed between or completely around the source of the input.
 * Cannot detect players sneaking.
 * Can be used with a piston to create a wireless redstone clock.
 * Emits particles ( Vibration JE1 BE1.gif ) when it senses a vibration nearby, except when waterlogged.
 * Are not affected by ambient weather such as rain, nor other sculk sensors and/or the warden.


 * Small Dripleaf


 * Appears highly varied in models.
 * Can be placed only in water or on clay, which counts as a 'moist' block.
 * Bone meal can be applied to turn it into Big Dripleaf.
 * Can be sold by the Wandering Trader.


 * Smooth Basalt


 * Spawns as an outer covering of amethyst geodes on the outer side of calcite, similar to real-life geodes.
 * Very similar in texture to calcite but different in color.
 * Can be obtained by smelting basalt in a furnace.


 * Spore Blossom


 * Can be placed on ceilings.
 * Sends particles downward when opened.
 * Creates ambient particle effects, similar to the nether biomes, but non-biome dependent, however, its natural generation is dependent of the Lush Caves, meaning that Spore Blossoms currently don't generate naturally in default worlds.


 * Tinted Glass


 * A type of glass that does not allow light to pass through.
 * Crafted with a glass block in the middle and 4 amethyst shards in a cross shape.
 * Drops itself when broken, even without Silk Touch, unlike glass.


 * Tuff


 * Spawns occasionally in the deepslate layer (below Y = 0).

Items

 * Amethyst Shard


 * Drops from amethyst clusters.
 * Used to make spyglasses and tinted glass.


 * Bucket of Axolotl


 * Obtained by using a water bucket on an axolotl, similar to fish.


 * Bundle


 * Can contain one cumulative stack of any variety of item types.
 * Stack sizes are sustained. For example, a bundle containing 32 blocks with a stack size of 64 could hold only an additional 8 ender pearls, as the stack size of an ender pearl is 16; the half stack of ender pearls added to the half stack of blocks is calculated as one full stack. Un-stackable items like minecarts remain un-stackable.
 * Displays a blue bar, similar to a durability bar, that shows how full it is.
 * Items are added by holding the bundle within the inventory and clicking an item or vice versa.
 * Tooltip shows icons of contained items.
 * Items drop to inventory when right clicked.
 * Are crafted with rabbit hide and string.


 * Copper Ingot


 * Created by smelting raw copper.
 * Can be used to craft copper blocks, lightning rods, and spyglasses.


 * Glow Berries


 * Grow from cave vines.
 * Can be eaten.
 * Used as a light source.
 * Loved by foxes as much as sweet berries.
 * Foxes can pick and eat glow berries from the vine similar to sweet berry bushes.


 * Glow Ink Sac
 * Drops from Glow Squid.
 * Used to make Glow Item Frames and glowing signs.


 * Goat Horn


 * Goats have a chance to drop this item when they ram into a block.
 * Holding while holding this item plays the raid horn sound effect.


 * Powder Snow Bucket
 * Using a bucket on powder snow creates a powder snow bucket.
 * Powder snow buckets can be used to place powder snow.
 * Powder snow buckets can also be filled from cauldrons filled with powder snow.


 * Raw Metals


 * Iron and gold ores now drop 1 raw iron and raw gold, as well as copper ore dropping 2-3 raw copper when mined instead of dropping themselves.
 * Can be smelted into their ingot variants.
 * The Fortune Enchantment works on iron and gold to drop more raw iron or raw gold.


 * Spawn Eggs


 * Spawn eggs for the new mobs are added.
 * Axolotl Spawn Egg JE1 BE1.png The axolotl spawn egg.
 * Glow Squid Spawn Egg JE1.png The glow squid spawn egg.
 * Goat Spawn Egg BE2.png The goat spawn egg.


 * Spyglass


 * Crafted from an amethyst shard and 2 copper ingots.
 * When while held, it allows the player to see far away objects through a small square.
 * By pressing F1, the player can zoom in the whole screen; avoiding the border that is normally presented when using.
 * Switching to third person view while using the spyglass shows the player holding up the spyglass to where the eyes would be.

Mobs

 * Axolotl


 * Based on the Mexican salamander with the same name in real life.
 * Planned to be found in bodies of water within lush caves biomes.
 * The first amphibian added to Minecraft.
 * Can be caught in a bucket like fish.
 * Comes in four common varieties, lucy (pink), wild (brown), gold, and cyan, and a rare blue variety, which has a $1/1200$ (~0.08334%) chance of spawning. This fraction is based on the fact that there are about 1200 axolotls left in the wild.
 * Plays dead when damaged, receiving Regeneration.
 * This regeneration ability is likely based on how real axolotls can regrow lost limbs.
 * Preys on fish, glow squid and squid, and attacks drowned and guardians (doesn't include Elder Guardians) if tempted with tropical fish by a player.
 * Axolotls prioritize hostile mobs over fish.


 * Glow Squid


 * Glow Squid.png


 * Originates from the mob of the same name in Minecraft Earth.
 * Underwater mob that behaves like a regular squid.
 * Can spawn in underground water sources.
 * Is attacked by axolotls without provocation.
 * Drops glow ink sacs when killed.
 * Does not affect the light level, but appears as if lit up. Glows in the same way that magma cube cores, vexes, blazes and the eyes of spiders, drowned, and endermen do.
 * Stops glowing for a short time and swims away quickly after taking damage.
 * Was decided on based on a mob vote between it, the Glow Squid from Minecraft Earth, and the Iceologer from the Minecraft Dungeons DLC Creeping Winter.


 * Goat


 * Spawns in mountain biomes.
 * Can jump high to avoid obstacles, about 5 blocks tall.
 * Attacks nearby mobs and players by charging and knocking them a considerable distance.
 * Mobs attacked by goats don’t attack back.
 * Doesn't attack other goats.
 * Takes reduced fall damage.
 * Avoids powder snow by jumping over it.
 * Can be bred with wheat, which produces a baby goat.
 * Drops one goat horn when ramming into a block. Goat horns do not regrow.
 * Has a 2% chance of spawning as a screaming goat, with different sounds.
 * Screaming goats use their ramming attack more often than normal goats.
 * Drops nothing upon death.

Non-mob entities

 * Glow Item Frames


 * A variant of the Item Frame that is made using a Glow Ink Sac.
 * Appears to glow but does not give any actual light.

World generation

 * Amethyst Geodes


 * An underground cave-like feature.
 * Generate in groups of 2-3 close together to each other in water, exposed. These are usually the only chances an amethyst geode can be exposed.
 * Contains smooth basalt, calcite, blocks of amethyst, budding amethyst, and the amethyst clusters they generate.
 * An amethyst geode that generates underwater causes water block textures to appear in openings. Placing or breaking a block next to the water blocks causes them to start flowing into the geode.
 * Twinkle-like sounds can be heard near amethyst clusters, which used placeholder sounds when it was showcased, and not the final version.


 * Ore veins
 * Large, rare, snake-like ore formations.
 * Copper ore veins mixed with granite generate above Y=0.
 * Iron ore veins mixed with tuff generate below Y=0.


 * Mountains


 * Height dependent generation.
 * Revamped, featuring some new small spruce trees on the slopes and ice and packed ice above the peaks.
 * Contain goats, rabbits, snow blocks, snow layers and powder snow.
 * Iron ore, emerald ore and coal ore are found in abundance.
 * Emerald ore no longer generates in veins of only one.
 * Can generate up to Y = 256.
 * New sub biomes Lofty Peaks, Snow Capped Peaks, Snowy Slopes, Mountain Grove, and Mountain Meadow.


 * Caves


 * Completely overhauled.
 * Now stretch down to Y = -59.
 * The cavern now generates in 2 layers of different stone bases depending on the depth.
 * Cavern layer above Y = 0 is made up of regular stone.
 * Stone transitions to deepslate from Y = 0 to Y = -7.
 * Deepslate now completely replaces stone from Y = -8 to bedrock.
 * Certain types of ores and structures still generate in the deepslate layer, as well as tuff.
 * Dirt, diorite, granite and andesite do not generate in this layer.
 * Biomes inside of caves introduced such as dripstone caves.
 * Contain aquifers, bodies of water with different heights, independent of sea level (Y=63).
 * Lava aquifers also exist, occasionaly replacing water aquifers below y = 0.
 * Improved old caves to blend in with the new generations of caves better.
 * New carver called crack carver, which appears as a fissure on the ground, like ravines but narrower and can go very deep.
 * New noise caves, coming in 2 forms, cheese and spaghetti.
 * The original caves still exist, mixing with the noise caves.
 * Cheese caves have large stone towers stretching from the bottom of the cave to the top.
 * Very large, often large enough to fly with an elytra.
 * Abundant with aquifers and ores.
 * Spaghetti caves are long, thin caves that have small aquifers and are more similar to original caves.


 * Mineshafts


 * For support, in the air, can generate with log pillars below or chains on fence posts above.


 * Strongholds


 * Try to generate fully encased in stone at low y-levels.

Biomes

 * Dripstone Caves




 * Contains pointed dripstone and dripstone blocks.


 * Lush Caves


 * Contain cave plants and moss.
 * Moss covers the ceilings and floors.
 * Clay pools generate inside.


 * Mountains


 * 5 new sub-biomes added:
 * Mountain Meadow
 * The lowest layer of a mountain.
 * Contain flowers and sweet berry bushes.
 * Mountain Grove
 * The second lowest layer of a mountain.
 * Covered in snow, snow blocks and powder snow, and is filled with spruce trees.
 * Rabbits spawn in this biome.
 * Snowy Slopes
 * The second highest layer of a mountain.
 * Covered in snow, snow blocks, powder snow and ice.
 * Goats spawn only in this biome.
 * Lofty Peaks
 * The highest layer of a mountain, generating if the mountain is high enough.
 * Generates if the surrounding biomes are too warm for snow capped peaks.
 * Covered in snow and ice.
 * Snow Capped Peaks
 * The highest layer of a mountain, generating if the mountain is high enough.
 * Generates if the surrounding biomes are too cold for lofty peaks.
 * Covered in snow, snow blocks, powder snow, ice and packed ice.

Gameplay



 * An action can cause vibrations in the air, which can be picked up by sculk sensors and wardens.
 * Can be caused by player and mob movements, blocks being placed or broken, containers opening, projectiles being fired and landing, blocks like pistons moving, buttons, levers and pressure plates activating, and blocks activating. Vibrations are not caused by ambient weather such as rain or snow.



General

 * Height limit
 * Has been increased to 384 blocks, expanding 64 blocks up and 64 blocks down, with 320 being the limit upward and -64 being the limit downward.
 * Ores
 * Most of the overworld ores have been retextured and touched up mainly for accessibility reasons. These also apply to the new deepslate ores.
 * This is a great help for color blind people that have difficulties distinguishing a certain ore of similar texture from another.
 * Diamond ore is an exception to this for being the "iconic" ore of the game, making Minecraft developers want to keep the classic feel of it.
 * Ore distribution has been changed for more strategic mining.
 * Certain ores are more common at certain depths, and some may generate in lower quantities or not generate at that level at all.

Planned additions
''Note that the names of many features are currently placeholders. They may be marked with the template .''

Blocks

 * Sculk Block.png


 * Generates in the mysterious new cave biome where the Warden lives, referred to as the "deep dark" temporarily.
 * Has an animated texture.
 * May be used in redstone.


 * Unidentified Sculk Block.png




 * Generates in the deep dark biome.
 * Has a different top texture than the Sculk Block and Sculk Chute.
 * May be used in redstone.


 * Sculk Something.png


 * Generates in the deep dark caves.
 * Made of sculk and a bone-like material.
 * May be used in redstone.
 * Glows but does not emit light, similar to the glow squid or the glow item frame.


 * Sculk Veins.png


 * Generates in the deep dark cave biome.
 * Generates in a layer on top of blocks, similar to snow.
 * Can be placed in all directions, like glow lichen.
 * Some have parts that are transparent, allowing the player to see the block it is on top of.
 * May be used in redstone as seen in this video when they talk about the sculk sensor.

Items



 * Warden Spawn Egg.png The Warden spawn egg is visually confirmed but not yet implemented.

Mobs

 * Warden.png




 * Spawns in the new Deep Dark biome.
 * The first fully blind mob (bats, despite relying almost exclusively on echolocation, still have basic eyesight).
 * When sensing movement, it moves toward the source of the movement.
 * Follows and attacks players, mobs, and other entities that make vibrations.
 * Does not attack other Wardens.
 * When attacked, it path finds toward the player.
 * Seems to follow the same rules as the sculk sensor when detecting noise.
 * When it detects a vibration, the growths on its head rattle and light up, similar to the sculk sensor.
 * If any projectile (e.g. egg, snowball, arrow) lands near the Warden, the mob inspects the location where the projectile landed, due to the projectile creating movement and noise. This feature can be used in order to cause a distraction.
 * Does not detect players that are sneaking.
 * Can detect players that are invisible.
 * When aggravated for long enough, the warden follows the player continuously, regardless of any other distractions.
 * Does not follow music from a jukebox.
 * Investigates explosion noises.
 * Incredibly strong, doing damage, bringing players wearing full netherite armor from full health to  health points.
 * A mob designed to be extremely difficult and fled from, rather than fought against. Players are meant to sneak around the Warden when traversing the Deep Dark, avoiding any vibrations that would cause it to detect them.
 * Has a way to counter the strategy of building up 4 blocks to avoid attacks.
 * At least as fast as the player's walking speed.
 * Seems to have considerable knockback resistance.
 * When near the warden, the brightness of the light the player sees decreases, regardless of Night Vision or brightness settings.
 * The warden's chest has a glowing core that appears to brighten and dim in tandem with the ambient lighting of the deep dark cave biome.
 * The core creates a low throbbing sound as it pulses. The sound and animation seem to speed up rapidly when the warden notices a player.
 * Is about 3.5 blocks tall, making it one of the tallest mobs in the game, exceeding the iron golem and enderman in height and width (the same).
 * This would also make it as tall as the wither (when hostile).
 * Currently burns in sunlight.
 * It is the only mob that spawns in the Deep Dark.

World generation

 * biome


 * New biome at the "deepest depths of the world".
 * Only spawns Wardens.
 * Contains sculk blocks and sculk sensors.
 * Exclusively generates within the Deepslate layer between -1 Y and -64 Y.
 * May contain candles.




 * Seems to be possibly a large tunnel-like cave generation.
 * Not much is known about this cave variation yet, but it was confirmed on Twitter by Henrik Kniberg.
 * Possibly contain "catacomb" style branching cave sections.
 * An improved version of mesh caves called noodle caves was added in 21w17a, being accessible via Caves & Cliffs world generation preview datapack.




 * More extreme and smooth terrain.
 * Likely change to the generation of alternate stone types, to make them appear in larger but less numerous deposits.
 * Possibly seen in a screenshot tweeted by Henrik Kniberg, in which diorite appears to generate in a long and flat horizontal strip, rather than a small unevenly shaped patch.
 * Ore generation further rebalanced, and influences the surrounding stone.

Gameplay



 * While in the deep dark cave biome, the ambient lighting, (such as the light given off by torches,) occasionally dims temporarily, limiting the player's visibility. This serves as a warning that the warden is nearby.

World generation
The underground generates with more variation and diversity than the surface.


 * Biomes


 * Dripstone Caves and Lush Caves generate in default worlds in Java Edition.


 * Mineral veins


 * Some stone appears a little different and when that stone is mined, more of the ore should be found behind it.




 * Other Stones


 * Diorite or calcite and what appears to be tuff spawn in layers of stone in straight lines instead of splotches.

Blocks



 * Spore Blossom


 * Can close.


 * Azalea Log


 * Between Java Edition snapshots 21w05a and 21w10a, many blocks (flowers, leaves, grass, ferns, sweet berry bushes, small dripleafs) had a block tag called "azalea_log_replaceable", possibly implying the existence of azalea logs.

Structures

 * Underground Cabin


 * Seen in the Deep Dark biome during the Minecraft Live 2020 stream.
 * Consists of a chamber with a cobblestone floor and stripped log support beams, containing 3 barrels, a blast furnace, and a large chest, with cobwebs and candles in and around it.
 * May possibly not be a generated structure, but instead a construction built for the purpose of the Warden showcase.

Bedrock Edition

 * Part I (1.17)
 * 1.17.1 was released exclusively on Nintendo Switch to fix the bug which cannot connect to any server.
 * 1.17.2 was released to fix bugs related to world generation.

Trivia

 * Swedish painter was one of the main inspirations behind the design and idea of the lush caves biome, specifically Bauer's 'Oskuldens Vandring' (Innocent's Journey) painting.
 * This is the first update:
 * To add a new ore to the Overworld since emerald ore was added in  for  and  for, in 2012 and 2014 respectively.
 * To add a real-world metal into the game since Classic 0.0.14a in 2009 for, which brought both iron and gold, and in 2012 for , which brought iron, not counting copper as an Element in Education Edition.
 * To add new shapes to cave generation since ravines were added in Beta 1.8 for and  for, in 2011 and 2014 respectively.
 * To add new types of rock to the Overworld since andesite, diorite and granite were added in Java Edition 1.8 and, both in 2014.
 * To be split $$ into two parts of development since the Adventure Update, which was split into Java Edition Beta 1.8 and Java Edition 1.0. $$, it is on the opposite quite common, the last split updates being Update Aquatic and Village & Pillage.
 * To increase the world height (from 256 blocks to 384 blocks normally, with custom world generation generation up to 2048 blocks) since Java Edition 1.2.1.
 * To have a mob vote since Update Aquatic.
 * To increase the depth of the bedrock floor underground since Java Edition Classic.
 * To add an amphibian mob to Minecraft.
 * Although the axolotl is the first amphibian mob implemented into Minecraft, it was not the first announced one, since frogs were announced during the MINECON Live 2019 biome vote.
 * Despite ores being shown to emit light during the reveal of this update, this was later confirmed to be just for demonstration purposes, to give a much clearer vision for viewers, and not for the final version.
 * It was confirmed to be a placeholder for glow lichen, a new light source.
 * The name "Sculk" is derived from the word "skulk", meaning "keep out of sight, typically with a sinister or cowardly motive".
 * Mojang Studios employees explored real caves to research for the update. This helped give inspiration and ideas for the update, including for the mesh caves.
 * Henrik Kniberg also recalled memories of past visits to caves around the world.
 * Tinted Glass is the name of Stained Glass in the April Fools' joke Minecraft 2.0.
 * During  snapshots, Waxed Lightly Weathered Cut Copper Stairs was the longest item name in the game, with 41 characters, between  and.
 * The art style of the concept art for Caves & Cliffs was inspired by the concept art of Diamonds and Lemons, the Adventure Time episode featuring a Minecraft crossover.
 * The reason for changing the name "Grimstone" to "Deepslate" was because the word "Grim" had too many connotations related to a negative feeling and therefore did not accurately describe the block as to what it actually was. The name "Deepslate" was eventually chosen because of the "journey" needed to gather it, as well as its location within the world.
 * Sculk sensors emit light when stepped on and/or receiving vibrations, similar to redstone ore.
 * Archaeology was originally planned to be added in this update, but was delayed to a later version when the update was split.
 * At the 0:24 mark of the Caves & Cliffs: Part I trailer, the Capricornus constellation can be spotted in the sky, which represents the sea-goat and is the Latin name for goat horn.

Gallery
Screenshots of the Caves & Cliffs Update from Minecraft Live 2020 and other sources: