View source for Nether Fortress

<!--Please do not change "nether fortress" to "Nether fortress", unless at sentence initials. According to [[Minecraft Wiki:Style guide#Do not capitalize]], structure names should not be capitalized.-->
{{For|the secret level in Minecraft Dungeons|MCD:Nether Fortress}}
{{Structure
| image = Nether Fortress.png
| biome = Any [[Nether]] biome
| blocks = *See {{slink||Structure}}
*See {{slink||Blocks}}
}}
A '''nether fortress''' is a large [[Generated structures|structure]] found in [[the Nether]], consisting of bridges, corridors, and towers. Nether fortresses are the only place where [[wither skeleton]]s and [[blaze]]s spawn, the latter of which's [[blaze rod]]s being required to craft and fuel [[brewing stand]]s and craft [[Eye of Ender|eyes of ender]] to access [[the End]]. It also features [[nether wart]] as loot, which is a key ingredient in [[brewing]].

==Generation==
Nether fortresses generate in all Nether biomes. To do so, the game splits the Nether into regions in which one of either a fortress or a [[bastion remnant]] can generate. The regions are 432×432 blocks {{in|Java}} and 480×480 blocks {{in|bedrock}}. 

[[File:Java Nether Structure Generation1.png|thumb|left|The Nether structure generation {{in|Java}}. The black lines represent each region and the dots represent coordinates. The green color is where they can generate and red is where they cannot.]]

Each region has a four chunk separation located on the south and east borders of the region in which neither a fortress nor a bastion can generate. 

[[File:Bedrock Nether Structure Generation.png|thumb|The Nether structure generation {{in|bedrock}}. The black lines represent each region and the dots represent coordinates. The green color is where they can generate and red is where they cannot.]]

This leaves only a 368×368 block section {{in|Java}} or 416×416 block section {{in|bedrock}} where a structure can generate. 

Two structures never generate in the same region, although they might overlap if they generate close to the separation border. {{IN|Java}}, the chance of a fortress generating instead of a bastion is {{frac|2|5}} (40%), while {{in|bedrock}} the chance of a fortress generating instead of a bastion is {{frac|1|3}} (33.3%).

Nether fortresses can generate buried in [[netherrack]]. In such a case, the interior is not filled with netherrack; all hallways and passages are clear except for open walkways and bridges. It is possible but rare for [[glowstone]] or crimson and warped [[huge fungi]] to generate inside the fortress pathways.

==Structure==
{{main|/Structure}}
Nether fortresses are large complexes composed of [[Nether Bricks|nether bricks]] that are supported by pillars that tower high above the [[lava sea]]s.

[[File:Enclosed Fortress.png|thumb|left|Segments of a nether fortress that are fully enclosed.]]

The fortress generation starts with a plain four-way crossing centered at chunk coordinates 11, ~, 11 of the designated [[chunk]].

[[File:Nether Fortress Crossroad.png|thumb|A crossroad found where walkways intersect.]]

A fortress has two areas, an exterior area of open bridges and an interior area of enclosed corridors. Both the bridges and corridors can end in a unfinished passway structure or may simply end without elaboration. Fortresses can tunnel through [[netherrack]], giving the "exterior" areas an appearance of tunnels with nether brick floor and netherrack walls and ceilings. At broken sections the terrain is not cleared, which may create a tunnel that leads straight into a wall of netherrack.

[[File:Blaze Fortress.png|thumb|left|The general pattern of the walkways.]]

[[File:Nether Brick Well.png|thumb|A lava well found inside a nether fortress.]]

The exterior consists of:
* <!-- NeBS --> Straight bridges.
* <!-- NeStart, NeBCr -->  Up to five plain four-way crossings.
* <!-- NeRC --> Up to four four-way crossings with arches made of nether brick and nether brick fences.
* <!-- NeSR --> Up to four small rooms with a single entrance and full-block "stairs" leading to the roof, which may have a single path leading out.
* <!-- NeMT --> Up to 2 blaze monster spawner platforms: structures consisting of three full-block "stairs" leading to a small platform fenced with nether brick fence, with a [[blaze]] [[monster spawner]] in the center.

[[File:Nether Fortress Large Stairs Room.png|thumb|Stairs in a nether fortress, with [[nether wart]] growing next to them.]]

The interior of the structures have 1×2 windows with [[fence|nether brick fence]]s as the windowpanes. The fences also form gate-like structures at the entrances of some rooms and corridors. Rooms include:
* <!-- NeCE --> The lava well room, which is the connection between the interior and exterior areas.
* <!-- NeSC --> Straight corridors.
* <!-- NeSCSC --> Up to five four-way crossings.
* <!-- NeSCRT, NeSCLT --> Up to 20 corridor turns (10 right-turns and 10 left-turns), each with a {{frac|1|3}} chance of having a [[#Loot|loot chest]] in the corner.
* <!-- NeCCS --> Up to three stairways made from actual stair blocks, leading downward.
* <!-- NeCTB --> Up to two three-way intersections with a small exterior balcony.
* <!-- NeCSR --> Up to two stairways leading up to a garden of [[soul sand]] and [[nether wart]] at the base of the stairs, a corridor leading away from the upper landing and a corridor behind the stairs. If the room is generated embedded in netherrack, only one block above the landing is cleared.

[[File:Nether fortress corridor crossing "area bounding blocks".png|thumb|right|An outline of the "bounding boxes".]]

===Blocks===
{| class="wikitable" data-description="Composition of a nether fortress"
!Block
|-
|{{BlockLink|Nether Bricks}}
|-
|{{BlockLink|Nether Brick Fence}}
|-
|{{BlockLink|Nether Brick Stairs}}
|-
| {{BlockLink|Soul Sand}}
|-
|{{BlockLink|Nether Wart}}
|-
|{{BlockLink|Chest}}
|-
|{{BlockLink|Blaze Monster Spawner|link=Monster Spawner}}
|-
|{{BlockLink|Lava}}
|}

The structure bounding box for the 4-way intersection is pictured above (top-down view), and consists of a 19 x 11 (height) x 19 volume centered on the floor block in the center of the intersection. This contrasts many of the other structure bounding boxes as their outlines tend to tightly follow the physical bounds of the structure.


==Mobs==
Fortresses use a list of possible [[mob]]s to spawn that is separate from the rest of [[the Nether]], regardless of the biome the fortress generates in. This includes [[zombified piglin]]s, [[skeleton]]s, and [[magma cube]]s, as well as two exclusive mobs not found anywhere else: [[blaze]]s and [[wither skeleton]]s.

[[File:Nether Fortress Blaze Spawner.png|thumb|left|A blaze monster spawner generated in the nether fortress.]]

Mobs spawn at a much higher rate if the fortress is surrounded by [[soul sand valley]] or [[warped forest]] biomes, as hostile mobs in these biomes (ghasts, skeletons, or endermen) spawn much less frequently, allowing most hostile mobs to spawn in the fortress.<ref>{{bug|MC-182170}}</ref>

=== Java Edition ===

In ''Java Edition'', the spawning algorithm has two checks:

#It checks if the spawn coordinates are within the "bounding box" of a single piece (e.g. corridor or walkway) of the fortress. <sup>(referred as "structure bounding box" above)</sup> In this case the block type of the ground does not matter.
#It checks if the spawn coordinates are within the "bounding box" <sup>(referred as "area bounding box" above)</sup> of the entire fortress and whether the ground consists of [[Nether Bricks|nether bricks]].

If either check passes, it uses the special mob list for fortresses rather than the list for the biome when choosing the mob to spawn. The actual mob spawning proceeds as normal for the mob chosen from this list.

{{Spawn table
|edition=Java
|monster=
{{Spawn row|name=Blaze|weight=10|size=2-3}}
{{Spawn row|name=Wither Skeleton|weight=8|size=5}}
{{Spawn row|name=Zombified Piglin|weight=5|size=4}}
{{Spawn row|name=Magma Cube|weight=3|size=4}}
{{Spawn row|name=Skeleton|weight=2|size=5}}
}}

=== Bedrock Edition ===

In ''Bedrock Edition'', instead of spawning anywhere within a structural bounding box, ''most'' mobs spawn only in ''structure spawn locations'' along varied-length lines spaced apart 4-11 blocks throughout the fortress. They are not set to a particular Y level other than "inside the structure" and are indeed columns several blocks high. They do not require any special type of block, any regular spawnable block will do. 

To identify these spawning columns, glass panes can be placed all over the fortress, 1 block above surface blocks. This will keep the mobs stationary. (This technique works in Bedrock due to mobs spawning in the northwest corner of blocks.) Note that these spots may be on top of the raised side blocks, so these side blocks have to be removed before a glass pane grid can be placed. 

[[Zombified Piglin]] spawns do not obey structure spawn locations; they can spawn anywhere in the fortress.

==Loot== 
{{see also|Chest loot}}
[[File:Nether Fort Chest.png|thumb|right|250px|A chest that generated in a nether fortress.]]

Fortresses generate nether fortress loot with chests in the indoor sections placed at some corridor turns.

{{LootChest|nether}}

==Advancements==
{{load advancements|A Terrible Fortress}}

==Video==
{{yt|BQJAebejadQ}}

==History==
{{History|java}}
{{History||1.0.0|snap=September 16, 2011|slink={{tweet|jeb_|114629982042591232}}|[[Jens Bergensten|Jeb]] tweets a teaser screenshot of changes to the Nether terrain generation, including fortresses.}}
{{History|||snap=September 19, 2011|slink={{tweet|jeb_|115736801347506176}}|Jeb releases a second teaser screenshot, showcasing the structure of the then upcoming fortresses.}}
{{History|||snap=September 21, 2011|slink={{tweet|jeb_|116549786051682304}}|Jeb mentions that he is finished with most of the new Nether features, including two new mobs, one of which is a "retexturing attempt".}}
{{History|||snap=Beta 1.9 Prerelease|Added fortresses.}}
{{History||1.4.2|snap=12w36a|[[Wither skeleton]]s and [[skeleton]]s now naturally spawn in fortresses.
|Other mobs also found in fortresses spawn less often due to that addition. [[Zombie pigmen]] became remarkably more uncommon though due to their weight being halved.}}
{{History||1.6.1|snap=13w18a|Chests now generate in fortresses.}}
{{History||1.8|snap=14w27a|Fortresses are now affected by the "Generated structures" option.}}
{{History|||snap=14w30a|Added possibility of obsidian in chests.}}
{{History||1.9|snap=15w43a|Reduced loot in chests from 2–5 stacks to 2–4.}}
{{History||1.16|snap=20w06a|Fortresses can now spawn in the [[soul sand valley]] biome.}}
{{History|||snap=20w15a|Fortresses can now spawn in the [[basalt deltas]] biome.}}
{{History|||snap=20w16a|Fortresses now generate evenly throughout the Nether.}}
{{History|||snap=Pre-release 3|Fortresses are now slightly more common.}}
{{History||1.20<br>(Experimental)|link=1.19.4|snap=23w04a|[[Rib armor trim]] are now found in fortress chests.}}
{{History|||snap=23w05a|Increased the chance of [[rib armor trim]]s being found in fortress chests from 4.7% to 6.7%.}}

{{History|pocket alpha}}
{{History||v0.12.1|snap=build 1|Added fortresses.}}
{{History||v0.15.0|snap=build 1|Horse armor can now be found in chest loot.}}

{{History|console}}
{{History||xbox=TU7|xbone=CU1|ps=1.0|wiiu=Patch 1|switch=1.0.1|Added fortresses.}}
{{History||xbox=TU9|Changed fortresses to make nether wart rooms more likely.}}
{{History||xbox=TU19|xbone=CU7|ps=1.12|Chests now generate.}}

{{History|new 3ds}}
{{History||0.1.0|Added fortresses.}}
{{History|foot}}

===Historical images=== 
<gallery>
Netherrack-first.jpg|The first screenshot of nether fortress.
Nbrick.png|A brightened version of the previous screenshot.
New_Nether_2.jpg|The second screenshot, showing a large complex of the nether fortress.
New_Nether_2_bright.jpg|The second screenshot brightened.
Overworld Fortress.png|A nether fortress in the overworld.
</gallery>

==Issues==
{{Issue list}}

==Trivia==
*In rare cases, a fortress may not generate any indoor rooms except one single lava room,<ref>{{bug|MC-194769||Nether Fortresses can generate without a lava room and corridor section.}}</ref> forcing the player to go to another fortress (or housing unit bastion) to find their first nether wart. This usually occurs when a portion of the exterior section of the fortress blocks the exit to the interior section of the lava well room.
*Sometimes, two or more fortresses can generate close to or even within one another, ultimately creating an even larger cumulative fortress.
*There is an opening out of the fortress under the lava well, with a single block of [[Nether Bricks|nether bricks]] from which the [[lava]] spreads out.
*The soul sand valley [[bone blocks]] and [[basalt pillars]] (down to within three blocks as-usual of a walkway) can replace more nether bricks.  Less-often, [[huge fungi]], [[nether wart block]]s, [[warped wart block]]s, [[crimson stem]]s, and [[warped stem]]s can replace nether brick, most visibly along walls.

==Gallery==
<gallery>
Netherwart.png|Some nether warts found at a stair.
Netherfortress.png|A demonstration of the pathway architecture and its ability to cut through netherrack.
BlazeSpawnerPlatform.png|The blaze monster spawner room.
OpenCorridor.png|The abrupt end of an inside corridor.
OutsideStructure.png|The broken passways.
Giantfort.png|A large amount of corridors. Notice how corridors do not develop arches in their supports.
Ghastinruins.png|A ghast that has spawned inside of one of the larger rooms.
TwoNetherFortresses.png|A player in a fortress with another nether fortress across from it.
Netherfortressstacked.png|A fortress with another one generated on top of it.
Lava Well.png|The lava well room.
Fortress2.png|A fortress in a [[warped forest]] biome.
Crimson Forest Fortress.png|A fortress in a [[crimson forest]] biome.
Netherfortressbasaltdelta.png|A fortress in a [[basalt deltas]] biome.
Large Nether Fortress.png|A large nether fortress.
Blaze preparing to attack.png|A [[blaze]] on fire, preparing to attack.
Blaze flying preparing to attack.png|A flying [[blaze]] ready to attack.
Wither Skeleton and Blaze.png|A [[blaze]] and a [[wither skeleton]] in a fortress.
Blazes and Wither Skeleton near a Spawner.png|A [[blaze]] and a [[wither skeleton]] next to a blaze [[monster spawner]].
Blazer Spawner.png|A blaze monster spawner room surrounded by netherrack.
File:Nether Fort Spy.png|[[Ari]] spying on a fortress using a [[spyglass]].
</gallery>

==References==
{{reflist}}

{{Generated structures}}

[[de:Netherfestung]]
[[es:Fortaleza del Nether]]
[[fr:Forteresse du Nether]]
[[ja:ネザー要塞]]
[[ko:네더 요새]]
[[nl:Netherfort]]
[[pl:Forteca Netheru]]
[[pt:Fortaleza do Nether]]
[[ru:Адская крепость]]
[[uk:Пекельна фортеця]]
[[zh:下界要塞]]