Tutorial:Defeating trial chambers
Trial chambers are large, procedurally generated structures found in the deepslate layer of the Overworld. They contain trial spawners, which drop loot when all their spawned mobs are defeated, allowing for a fairly tough group experience.
Benefits of taking on a trial chamber
- To get the trial key and its ominous variant, used to unlock vaults and ominous vaults respectively.
- To get loot from supply chests, barrels, and decorated pots scattered throughout the structure.
- To get loot dropped by trial spawners and all the spawned mobs.
- To get the heavy core and breeze rods to craft the mace. Both the core and rods can be obtained only from trial chambers.
- To get the guster and flow banner patterns, two types of smithing templates, three types of pottery sherds and three music discs exclusive to this structure.
- To get the large amount of copper blocks generated throughout the structure, which is more efficient than mining a large copper ore vein, as no smelting is needed to obtain the copper.
- To get a trident without having to kill hundreds of drowned.
- To obtain your first slimeballs, so you can brew some Oozing potions and build an Oozing slime farm.
- To get the hoppers and copper bulbs generated throughout the structure, so you don't have to spend your iron or blaze rods to craft them.
- To access snowballs, dead bushes, cacti, moss, mangrove trees and pointed dripstone without visiting the respective biomes.
- To access biome-specific mobs like boggeds, husks and strays without having to go to their own biomes and wait for night, as well as breeze, a mob exclusive to trial chambers, helping you to achieve the "Monsters Hunted" advancement (kill one of every hostile mob).
- To obtain potions of Weakness, allowing you to cure zombie villagers before accessing the Nether.
- To convert the trial chamber into a farm for trial keys.
- To convert the trial chamber into a mob-free base, as regular hostile mob spawning is disabled here.
Preparation checklist
At least an iron sword, preferably enchanted, or an 
axe (or both) if you play Java Edition.
A good bow and at least a stack of arrows (or just one if your bow has Infinity). Decorated pots, barrels, and chests may contain arrows to replenish the arrows you use; also, chambers usually contain a lot of spawners of ranged mobs, which drop arrows on death.
At least a full set of iron armor, preferably enchanted.
A pickaxe, preferably iron or better if you have the materials.
Some golden apples (optional but recommended)
Highly nutritious food, such as cooked porkchops or steak, at least half a stack. Trial spawners eject food as loot, but it's unlikely that this food will be enough on its own to keep you at full health.
At least 16 logs for crafting.
A few stacks of easily breakable building blocks, such as cobblestone and netherrack, to block off passageways, pillar up, seal trial spawners, and mark out areas you already visited.
A shield in the offhand to defend against mob attacks, or a totem of undying if you have any.
Some ominous bottles, needed to start an ominous trial, which results in better loot, and is the only way for obtaining the heavy core (optional, only if you're well prepared).
A few bundles, to organize the loot you obtained and save valuable inventory slots.
Some signs or hanging signs to show directions and mark areas (optional, can be crafted with the logs you bring).
Finding trial chambers
Trial chambers only generate underground, making them a bit difficult to find. The simplest method of finding them is to buy a trial chambers explorer map from a journeyman-level cartographer villager. This costs 12 emeralds and 1 compass (default price). If you do not have access to a village, you can either mine underground and hope to stumble upon trial chambers, or travel through caves until you find trial chambers which are exposed to the air.
An advanced technique exclusive to Java Edition is to use the debug menu and pie chart, which detects presence of trial spawners and vaults within render distance. This distance can be lowered to narrow down the searching area.
Additionally, using cheats, you can use the /locate structure trial_chambers command to locate the nearest trial chambers.
Acquiring ominous bottles
Optionally, you can increase the difficulty and loot reward of the chambers by drinking an ominous bottle before taking on a trial spawner. These drop from either raid captains (in pillager patrols or outposts, but not during raids), or from normal and ominous vaults in trial chambers.
Defeating the trial chambers
Once you have an explorer map, dig down to the chamber. Try to find a safe spot to set up a base of operations, preferably near the "entrance" or one of bed rooms. If you want to take on an ominous trial, you have to drink one of the ominous bottles you've brought.
At the center of each trial chamber, there is a big corridor that branches off into hallways leading to combat chambers. Since the corridor connects all other rooms, it is recommended to beat all the trial spawners in it before going in other rooms.
Once you're ready to take on the chamber, you can explore it room by room. You may want to use blocks such as cobblestone or wood that are not native to the trial chamber to mark off rooms you've already been in. Another way to mark explored rooms and paths is to use hanging signs found in barrels around the structure. Throughout the structure, usually near entrances to rooms, there are empty barrels with hoppers that can be used for inventory managing and storage.
When you find a combat chamber with trial spawners, you can build a small shelter to retreat to if things get tough. There are four types of spawners found in any trial chamber:
- a "melee" mob (which can be a zombie, husk, or spider);
- a "small melee" mob (a slime, silverfish, cave spider or baby zombie);
- a "ranged" mob (a skeleton, stray or bogged);
- and a breeze (which can only be found in certain combat chambers)
Each of them has its own strengths and weaknesses. For most mobs, it's safer to take them out from a distance, using a bow; this doesn't work for breezes, which reflect the projectile back at the attacker. For a tutorial on combating mobs in general, see Tutorials/Combat.
Certain combat chambers contain dispenser traps, which can be activated by breezes or by the player using wind charges.
If you've chosen to use ominous bottles, the trials will be significantly more difficult. Mobs which can spawn with armor (skeleton and zombie variants) more often spawn with armor, usually enchanted - this includes even diamond armor. They also hold a better weapon, either a sword or an enchanted bow. Mobs which can't spawn with armor (arthropods, slimes and breeze) instead spawn more numerously.
Additionally, ominous spawners shoot projectiles at the player and mobs: lingering potions, wind charges, arrows, tipped arrows and fire charges. Potions have one of seven effects: 
Wind Charged, 
Oozing, 
Weaving, 
Infested, 
Strength, 
Speed, or 
Slow Falling. They can either benefit or harm the player, but they also can do the same to mobs. Tipped arrows inflict either Poison I or Slowness IV.
Once all mobs from a spawner have been killed, you defeated it, and a reward pops out of the top - it can be either a food item or a trial key / ominous trial key if the spawner is ominous. You can come back 30 minutes later to fight the spawner again.
Vaults are usually placed inside combat chambers, so it is recommended to defeat all trial spawners in the room before opening them. Ominous vaults are placed near the ceilings of the rooms, there is always one ominous vault in each combat chamber, and at least two ominous vaults in the main corridor.
After defeating the trial chambers
After you've defeated the trial chambers, you can build up infrastructure near the chambers to make them easier to access. One way to do this is to build a stairway down to the chambers that enters through the entrance corridor.
Because of the ridiculous amount of copper blocks found in this structure, it is worth it to tear down the structure instead of mining for copper (particularly because of how many decorative blocks are in the copper family.). As a side effect, it can be easier to convert trial spawners into farms for keys. It makes future trial chambers much easier to tackle when you already have lots of keys.
