Nether fortress

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Nether Fortress
Nether Castle.png

The Nether

Consists of

See Structure

First appearances

See history

Nether fortresses are structures that are naturally generated in the Nether.

Generation[edit | edit source]

A nether fortress generated in the ground.

Nether fortresses tend to cluster together in strips that run along the Z-axis (north and south). Players who travel along the X-axis (east or west) will have the best chances of finding one; those who travel north or south may travel for hundreds or thousands of blocks before discovering a fortress.

Nether fortresses may be generated in inconvenient places, where half of or even the majority of the fortress is buried in netherrack. The interior will not be filled, however; all hallways and passages will be clear except for open walkways and bridges. It is rare, but possible for glowstone to generate inside of the fortress pathways.

Mobs[edit | edit source]

A blaze spawner generated into the side of some netherrack.

Nether fortresses use a list of possible mobs to spawn that is separate from the rest of the Nether. Nether fortresses spawn magma cubes at a much higher rate, and also spawn two exclusive mobs which cannot be found anywhere else: blazes and wither skeletons. Normal skeletons have a 20% chance to spawn in place of a wither skeleton. Ghasts do not spawn in fortresses.

Blazes are desired because of their main loot—blaze rods, as well as the high amount of experience they drop. Wither skeletons are mostly desired for their wither skeleton skulls, which are necessary to create the wither.

The spawning algorithm has two checks:

  1. It checks if the spawn coordinates are within the "bounding box" of each piece (e.g. corridor or walkway) of any fortress.
  2. It checks if the spawn coordinates are within the "bounding box" of the entire fortress, and that the block under the spawn location is nether brick.

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

Structure[edit | edit source]

The general pattern of the walkways.
A lava well found inside nether fortress.

Nether fortresses are very large bridge-like complexes, composed mainly of nether bricks, that are supported by massive pillars that tower high above the lava oceans. A nether 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 "broken" structure or may simply end without elaboration. Nether 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.

The exterior consists of:

  • Straight bridges.
  • Up to 5 plain four-way crossings.
  • Up to 4 four-way crossings with arches made of nether brick and nether brick fence.
  • Up to 4 small rooms with a single entrance, and full-block "stairs" leading to the roof which may have a single path leading out.
  • Up to 2 blaze spawner platforms: structures consisting of three full-block "stairs" leading to a small platform fenced with nether brick fence, with a blaze spawner in the center.
Stairs in a nether fortress, with nether warts growing next to them.

The interior of the structures have 1×2 windows with nether brick fences as the windowpanes. The fences also form gate-like structures at the entrances of some rooms and corridors. Rooms include:

  • The lava well room, which is the connection between the interior and exterior areas.
  • Straight corridors.
  • Up to 5 four-way crossings.
  • Up to 20 corridor turns (10 right-turns and 10 left-turns), each with a 13 chance of having a loot chest in the corner.
  • Up to 3 stairways (made from actual stair blocks) leading downwards.
  • Up to 2 three-way intersections with a small exterior balcony.
  • Up to 2 stairways leading up to an open landing, which have patches 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 generates embedded in netherrack, only one block above the landing is cleared.

Blocks[edit | edit source]


Nether Brick

Nether Brick Fence

Nether Brick Stairs

Soul Sand

Nether Wart


Blaze Spawner


Loot[edit | edit source]

See also: Chest loot
A chest that generated in a nether fortress

Nether fortresses generate nether fortress loot with chests in the indoor sections placed at some interior points where corridors turn at right angles.

Each Nether fortress chest contains 2–4 item stacks, with the following distribution:

Stack Size Weight # Items Chance # Chests

Gold Ingot
1–3 1573 1.233 49.8% 2.0

1 1073 0.411 35.7% 2.8

Gold Horse Armor
1 873 0.329 29.4% 3.4

Nether Wart
3–7 573 1.027 19.2% 5.2

Iron Ingot
1–5 573 0.616 19.2% 5.2

1–3 573 0.411 19.2% 5.2

Flint and Steel
1 573 0.205 19.2% 5.2

Iron Horse Armor
1 573 0.205 19.2% 5.2

Golden Sword
1 573 0.205 19.2% 5.2

Golden Chestplate
1 573 0.205 19.2% 5.2

Diamond Horse Armor
1 373 0.123 11.8% 8.5

2–4 273 0.247 8.0% 12.5

Video[edit | edit source]

History[edit | edit source]

Official release
1.0.0 September 16, 2011 Jens Bergensten tweets a teaser screenshot of changes to the Nether terrain generation, including nether fortresses.
September 19, 2011 Jens releases a second teaser screenshot, showcasing the structure of the upcoming nether fortresses.
September 21, 2011 Jens mentions that he is finished with most of the new Nether features, including two new mobs, one of which is a "retexturing attempt".
Beta 1.9-pre1 Added nether fortresses.
1.4.2 12w36a Wither skeletons and skeletons will now naturally spawn in nether fortresses.
1.6.1 13w18a Chests will now generate.
1.8 14w27a Nether fortresses are now affected by the "Generated structures" option.
14w30a Added possibility of obsidian in chests.
1.9 15w43a Reduced loot in chests from 2–5 stacks to 2–4.
Pocket Edition Alpha
0.12.1 build 1 Added nether fortresses.
Console Edition
TU7 CU1 1.0 Patch 1 Added nether fortresses.
TU9 Changed nether fortresses to make nether wart rooms more likely.
TU19 CU7 1.12 Chests will now generate.

Issues[edit | edit source]

Issues relating to “Nether fortress” are maintained on the issue tracker. Report issues there.

Trivia[edit | edit source]

  • Often, nether fortresses generate with no nether wart gardens in them at all. In some rare cases, a garden will have generated, but the nether wart will be partially or totally destroyed by falling lava.
  • In extremely rare cases, a nether fortress will not generate any indoor rooms except one single lava room.
  • Sometimes, two or more nether fortresses can generate very close or even within each other, ultimately creating an even larger cumulative nether fortress.

Gallery[edit | edit source]