Ghast

Ghasts are very large jellyfish-like mobs that float through the air and shoot fireballs from their mouths. Their bodies are 4 by 4 by 4 block cubes with 9 tentacle-like limbs hanging from the bottom. They first appeared in the Halloween Update. Ghasts are able to spawn anywhere in the Nether, as long as there is sufficient space (5*5*5 space is required to spawn) and the game is not in Peaceful mode.

Behavior
Ghasts normally float around with their eyes and mouth closed and periodically make high-pitched, child-like sounds. They open their eyes and mouth when attacking. They make a chirp-like noise when shooting and scream loudly when taking damage. The sounds that Ghasts make have a minimum intensity regardless of their distance, so they often sound closer when they are actually far away. As of Beta 1.8.1, the Ghast will let out a death rattle upon being killed - similar to the death cries that Zombies and Spiders use when killed. Fireballs do not home in and can be deflected by the player. This makes the fireballs fairly easy to deflect, assuming the player knows they are coming.

Unlike most other aggressive mobs, the Ghast does not have a pursuit mode - it does not attempt to draw closer to the player when at long range (and likewise is not particularly likely to float away). Compared to other mobs, the Ghast has a very long search range and can target a player up to 100 blocks away. When the player comes within about sixteen blocks, the Ghast will open range and attempt to gain altitude.

Ghasts will not fire at the player without a line-of-sight - this can be blocked by Glass, Glass Panes, Leaves, Nether Portals, Vines, Iron Bars, both types of Fences, and Cobwebs - making safe scenic paths through the Nether a viable possibility. When not moving, Ghasts within firing range will face the player, giving the impression that they can see through transparent materials. Ghasts can draw a line-of-sight through curtains of lava, and their fireballs can pass through it meaning players near a pillar of lava can be struck without seeing the source. However, the Ghast can "cancel" its fireball while shooting if the player moves behind an obstruction or builds one.

Ghasts may drop a Ghast Tear when killed, but this can be hard to collect - because it is a flying mob, the tear may fall into lava or an inaccessible area. Ghast tears are a positive potion ingredient, for many useful potions, so Ghast tears are well worth obtaining.

If shot at by a Ghast just try to hit the fireball back at the ghast, if you happen to hit the ghast it will die in one hit.

Ghast Fireball
The Ghast's fireball attack has a straight trajectory unaffected by gravity and an unlimited or very long range limited in practice only by the confines of the Nether's caverns. Their explosions can often be heard without the impact being seen. At close range, it is the most powerful mob attack in Minecraft, along with the blast of a Creeper. A direct hit from point blank range will deal a full 10 hearts of damage but damage decreases with distance and is less if the player is simply caught in the blast radius. Additionally, the projectile is fairly slow and aims slightly above the player's head. When two Ghast fireballs collide, one is deflected to a random direction while the other explodes upon impact. Hitting a Ghast fireball with an item held in hand, an empty hand or a fired arrow will deflect the fireball in the direction of the player's aim. Charged arrows may destroy the fireball instead of deflecting it.

If a Ghast's fireball hits a portal or hits close to it the portal will be closed, requiring re-ignition. If the player manages to get a Ghast to fire at the portal while it is closed, it can be reignited using the fireball. Blocks are also set on fire by the explosion, adding an extra hazard to fighting Ghasts.

The minimum block resistance required to absorb all blast force of the Ghast's fireballs is 20.17, meaning that fences and other blocks with low blast resistance will be destroyed in a fireball explosion.

Fighting Ghasts
Ghasts are often considered the most difficult mob to kill in the nether owing to their extreme attack range, explosive attack power, mobility and flight. They are also quite common; players in any exposed area will have to deal with them sooner or later and possibly from the moment they step out of a portal. Ghast fireballs have a profound effect on Nether architecture, making a compelling case to use only materials resistant to their explosions for outer walls and exterior fittings in places where their fire may be drawn. A Ghast's firepower is highly inaccurate at most ranges if one is moving. Players are most vulnerable when they are building in the Nether, when they may well not be moving and possibly standing above a long fall. Ghasts can break blocks from under the player, often dropping them into lava or causing death through falling damage.

The player can deflect fireballs by hitting them with anything before they impact, even bare hands. Because of their low speed, spamming mouseclicks is often enough to deflect any given attack. It is possible to kill Ghasts by deflecting their attacks back at them, but it can be difficult since Ghasts are agile and their hitbox is restricted to their tentacles. A deflected fireball is able to kill any ghast in one hit. You can easily deflect a fireball in the direction you want by shooting an arrow, fishing rod, or snowball at the fireball. The fishing rod, when released, slightly affects the fireball's trajectory. This relationship goes both ways and a Ghast's constant stream of fireballs may well interfere with the firing arc of your bow.

Most Ghast kills are made with a Bow and Arrows for obvious reasons but a Ghast can be killed with melee weapons if the player can get close enough before it draws away. Ghasts are highly vulnerable when caught on the ground since their attacks can be deflected and their health is quite low - 2 blows from a diamond sword will destroy one. It is possible to use a Fishing Rod to draw Ghasts near enough to hit them with a Sword. A close Ghast is also much easier to hit with a bow, though reaction time against its fireballs is likewise lessened. When aiming your bow, be sure to lead your shots as Ghasts can quickly change trajectory and move quite quickly. Depending on the Ghast's range and relative altitude, it is usually necessary to also aim at a high trajectory to gain extra range. Where possible, having the advantage in altitude (such as shooting from the topmost layer of the Nether) is of enormous help. The Ghast's hitbox is mainly its tentacles, and aiming too high may cause a shot to go through the Ghast's body, dealing no damage.

Much like using neutral or enemy mobs as shields against arrows fired by skeletons in the regular world, it is feasible to use Zombie Pigmen as shields against Ghasts in the Nether. It is possible to injure or kill zombie pigmen in this fashion without ever making them hostile to the player.

An effective method of fighting Ghasts in the nether is to make a shelter, preferably out of brick, cobblestone, obsidian, or other explosion-resistant materials. Make a 1x1 hole in the roof and add ladders leading up to it, in such a way that you can poke the upper half of your body through the roof. When a Ghast is near, climb the ladder, shoot an arrow at the Ghast and quickly descend again into your explosion-proof shelter. This should mean that you can kill Ghasts easily with minimal health loss. To improve this even further, add a small 3x3 roof 1 block above the hole in the main roof. Most of the Ghasts' fireballs will now hit this roof rather than you, meaning that you should be safe against most Ghast attacks.

Resistance to Fire
Ghasts may also be set on fire, but Fire and Lava don't actually damage them. A similar effect is seen with Zombie Pigmen. When a Ghast is caught in lava, its movement is impeded, and can then be easily targeted with arrows. At around 23:09 in this video, a Ghast impeded by a lavafall can be seen, and again, but closer and for a longer period of time, at 23:59.

It is disputed that Ghasts can be killed by lava or fire if continually re-exposed. This is achieved by a Ghast floating in and out of lava. There have been reports of zombie pigmen dying while in lava, due to the fact they "bob" in and out of lava,(a rumor about zombie pigman is that in the lava they gain fall damage which affects them when they exit the pool of lava.) which raises doubt that Ghasts and zombie pigmen are completely lava/fireproof.

History

 * Ghasts were introduced in Alpha 1.2.0
 * Ghasts and Zombie Pigmen were the first mobs introduced to the Nether.
 * Ghasts used to be vulnerable to fire and lava, but since the Alpha 1.2.2 update, this bug has been fixed and they no longer get hurt when they come in contact with lava or fire.
 * Prior to Beta 1.7 Ghasts aimed at the camera, not the player. Pressing F5 allowed one to easily send the fireball over their head instead of at the character.
 * In Beta 1.6 to 1.8, Ghasts' fireballs did not cause fires, due to a bug.
 * Ghasts used to not be affected by light, and appeared with the same brightness anywhere. This was changed in Beta 1.9 Pre-release.
 * Since 1.9, Ghasts are able to be killed by their own fireballs, allowing the achievement "Return to Sender."
 * Prior to 1.9 you could only injure Ghasts by hitting their tentacles, as their hit box was not large enough to incorporate the body.
 * Prior to 1.0.0, Ghasts used to shoot fireballs with a snowball texture. In 1.0.0, a texture unique to fireballs was added.

Trivia

 * Contrary to popular belief, Ghasts will spawn on blocks. Therefore they can't spawn on transparent blocks no matter how high the roof is. If any transparent blocks protrude into their spawning area (5x5) they cannot spawn.
 * As of 1.1 in .minecraft/resource/newsound/mob/ghast, Ghasts have an affectionate scream, which is a high pitched horn sound (like the classic cartoon tugboat sounds).
 * In Creative Mode, you can go inside of a Ghast by falling through the top of it.
 * Originally, Ghasts were intended to be able to spawn near Nether Portals in the Overworld. However, this ability has not yet been implemented.
 * Despite being fireproof, Ghasts and Zombie Pigmen are capable of drowning if under water or lava for too long. This means they, like the player and other mobs, require air to live.
 * Ghasts can cause other mobs to attack it, but the Ghast will never target other mobs; it will only target the Player.
 * It is possible to kill Zombie Pigmen by deflecting Ghasts' fireballs at them. It is also possible to deal a Critical hit on a fireball, since it is an entity.
 * Prior to the full release of Minecraft, when a Ghast shot a fireball, it looked like a flaming snowball; it has since been updated with a new magma stone texture.
 * Ghasts are the largest mob by volume - they are eight times as big as the largest variation of slime, but Ender Dragons are longer.
 * It is impossible to 'ride' a Ghast as the player will fall right through it.
 * If a Ghast is trapped in a cube, it will shoot fireballs through the cube. This is because like all other things that shoot, it spawns the projectile one block in front of it.
 * Due to the explosive property of Ghast fireballs, they can be used to mine blocks in the Nether.
 * Ghasts (like all other flying mobs, including the Player in creative mode) can actually fly much higher than y-coordinate 128.
 * Using a tool to spawn a mob riding a ghast will cause the mob to be inside the ghast, unless it's a giant.
 * Ghasts take damage from touching cacti.* Similarly, for Ghasts on fire, the flame texture will enlarge on the Ghast.
 * Some rooms in Nether Fortresses are big enough for a Ghast to spawn in. However, this Ghast will likely be trapped, as there may not be an exit large enough for it to fit through.
 * A Ghast's eyes appear to be full of tears, it is unknown why they are constantly crying/sobbing.
 * Ghasts, even though they can fly, will not spawn above water if it is hacked into the Nether.
 * If a Ghast is killed, any Fireball the Ghast has launched will disappear.
 * Their fireballs can destroy Block 97, but this would kill the silverfish inside of the stone block instead of spawning it.
 * In 1.1, Spawn Eggs are the only way to see Ghasts in the Overworld without hacks.
 * If you tweak a Mob Spawner to spawn Ghasts, the model inside the spawner is larger than the frame.
 * Ghasts appear to be 4x4x8 blocks high, but since their hitbox only covers the lower half of their body, they are technically 4x4x4 blocks
 * A well timed arrow can knock back the projectile into the ghast.

Bugs

 * Sometimes, if there is a 1-4 space between a platform, they will be trapped, but will still be able to fire at you.
 * Their hitbox data seems out of place. Objects will pass through the top of a Ghast, however, hitting its tentacles will hurt it.
 * Arrows will sometimes pass through the Ghast during server lag in SMP.
 * If spawned in the Overworld (by using hacks) in a glass cage, they will float and stare at the player, but Ghasts will sometimes unexpectedly shoot a fireball in the direction of the player even though there is a glass barrier between them and a player. This bug appears to be absent in the Nether.
 * A fireball will not disappear if in flight when switching to peaceful.
 * Ghasts' explosions are less "connected" to them in SMP than in SSP. For this reason in SMP mobs damaged by a Ghast's fireballs will not attempt to attack the Ghast and Ghasts that are either spawned or follow a player into the surface world (see below) can become divorced from their explosions and become an essentially peaceful mob. Similarly, Ghast explosions can sometimes follow a player into the real world, without any nearby Ghasts, but these normally only appear in the form of apparently random explosion noises not connected to actual damage causing explosions.
 * It is possible to deflect a ghasts fireball with a fishing hook, which will cause your line to move with the deflected fireball.
 * Sometimes, attacking a Ghast may not make it attack you when you are at a range of 16 blocks or less.
 * If you get too close and touch the ghast, it is so big that you will see yourself inside the ghast, and the body wall and the stubs of tentacles sticking out of the bottom.
 * In SMP, after being bumped by a passive mob in the Nether (especially whilst standing in a waterless chicken farm), Ghasts have the ability to target the player through walls and shoot fireball after fireball, creating a tunnel to the player, killing said player. Ghast continues to fire until the player respawns, which can result in anything flammable burning, chests exploding and more. Recreated twice, 20 blocks underground.