Trial Chambers Explained: Vaults, Keys and Ominous Mode

Trial Chambers are underground dungeons of tuff bricks and copper, added in 1.21. One chamber pays out twice: clear it normally and open the Vaults, then drink an Ominous Bottle inside and clear it again for the Ominous Vaults.

Finding a Trial Chamber

• The structure starts from a corridor end placed between Y=-40 and Y=-20. Most of its rooms sit higher, between about Y=-20 and 0.
• Chambers generate in every Overworld biome except the Deep Dark. The game tries to place one in each 34 by 34 chunk region, which is 544 by 544 blocks.
• In a world started before 1.21, they only appear in newly generated terrain.
• A Journeyman Cartographer can sell a map to one for 12 Emeralds and a Compass. Each Cartographer offers two of its three possible Journeyman trades, so try another if yours lacks it. Since 26.3 the map is its own item, the Buried Trial Chambers Map (formerly a map named "Trial Explorer Map"), and it can also turn up in the secret chest some Abandoned Camps hide.
• The seed map marks each region's placement spot for your seed without a biome check, so a marker in the Deep Dark stays empty. The trial chamber seeds list has worlds with one near spawn. With cheats on, /locate structure minecraft:trial_chambers prints the nearest.

What's inside a chamber

• Entrance: a Vault and chests that can hold a spare Trial Key, at under 3% per roll.
• Corridors: Decorated Pots (same small key chance), arrow dispensers and some Trial Spawners. Both corridor ends hold an Ominous Vault.
• Combat rooms: the main fights, each with one Ominous Vault.
• Intersections: two of the three designs hold an Ominous Vault.
• Supply cache: a rare hallway nook, missing from many chambers, with a chest of arrows, food, potions and sometimes a Milk Bucket.

Most rooms with a Trial Spawner also hold at least one Vault. Some corridor spawners and some combat rooms have no normal Vault. Expect 6 to 8 Ominous Vaults per chamber on average.

Trial Spawners: the fights

A Trial Spawner wakes when it has a line of sight to you within 14 blocks. Light level makes no difference, and its mobs never despawn. Each chamber picks one mob per group when it generates, so all its spawners of a group spawn the same mob.

A wave grows when another player comes into range and never shrinks if they leave. Ordinary hostile mobs never spawn in the rooms, so you need not light them.

Two seconds after the last mob dies, one coin flip decides the reward for every player the spawner detected: a 50% chance that every player gets a Trial Key, otherwise each player gets food or a potion. Solo, about half your spawners give a key. The spawner then sleeps for 30 minutes, even while you are away.

Vaults: one opening per player

Use a Trial Key on a Vault. It ejects 2 to 5 drops and remembers you, up to 128 players. Each Vault opens once per player. A Vault you already opened rejects the key, and you keep it. A group of four takes four times the loot from the same room.

Ominous Vaults are Vaults in their ominous state, placed when the chamber generates. Trial Omen never turns a normal Vault into one. They sit on a small altar with Red Candles and Red Glazed Terracotta and only accept an Ominous Trial Key.

Odds per opening:

The Heavy Core and the Wind Burst book drop nowhere else.

Running the chamber ominous

1. 1.Clear it normally first. Fight every spawner, collect the Trial Keys and open every Vault.
2. 2.Get an Ominous Bottle. A Pillager captain, the one wearing the banner, drops one at a random level, I to V, if it leads a patrol or guards an outpost. Captains in a raid drop no bottle. Normal Vaults also drop bottles.
3. 3.Drink it in the chamber. You get Bad Omen for 100 minutes. Walking into a village with Bad Omen starts a raid (see how to beat a raid).
4. 4.Let a spawner see you. Bad Omen turns into Trial Omen, which lasts 15 minutes per level, so 75 minutes from a level V bottle. Every spawner that sees you turns ominous and skips any cooldown left from your first run, so the whole chamber is live again.
5. 5.Clear the ominous waves. Each cleared ominous spawner has a 30% chance to give every player an Ominous Trial Key. Otherwise each player gets better food or a Potion of Regeneration or Strength.
6. 6.Open the Ominous Vaults with those keys.

Ominous waves also hit harder:

• Zombies (baby Zombies included), Husks, Skeletons, Strays and Bogged can spawn in chainmail, iron or diamond helmets and chestplates enchanted with Protection IV, Fire Protection IV and Projectile Protection IV at once. The melee mobs carry swords, the archers bows. None of that gear drops.
• Every 8 seconds the spawner hangs one item above you or one of its mobs, then drops or fires it. Each ominous spawner picks from a fixed pair: a lingering potion (Wind Charging, Oozing, Weaving, Infestation, Strength, Swiftness or Slow Falling) and a projectile (a plain, Poison or Slowness arrow, Fire Charges or Wind Charges).

An ominous spawner turns back into a normal one after its 30-minute cooldown.

Mistakes that waste a run

• Drinking milk during Trial Omen. Milk clears every effect, Trial Omen included, so don't use it on Poison from Bogged arrows.
• Drinking the bottle mid-fight. A spawner that turns ominous mid-wave despawns the mobs it sent and starts a fresh ominous wave, so the normal reward is lost. Drink between fights.
• Walking in on a level I bottle. Fifteen minutes is tight for a whole chamber.
• Mining the blocks. Trial Spawners and Vaults drop nothing when broken.
• Shooting Breezes. A Breeze deflects arrows back at you. The Breeze and wind charges guide covers the fight.

What to do with the loot

A Heavy Core above one Breeze Rod crafts the Mace. The mace guide covers smash damage and enchantments. Combine four Wind Burst I books on an anvil for level III. Keep the level III to V Ominous Bottles from Ominous Vaults: each is worth 45 to 75 minutes of Trial Omen. For the next chamber, pick another seed map marker or buy from a different Journeyman Cartographer, since every map one villager sells leads to the same place.