A trial chamber is a copper-and-tuff complex of fighting rooms that generates underground across most of the Overworld, roughly between Y=-40 and Y=0. It is the only structure in the game designed to be visited more than once, and it is the only place the heavy core — and therefore the mace — comes from.
It is also the safest good-loot structure in 1.21.4. Nothing in a chamber is as dangerous as a warden or a bastion, and the mobs arrive in fixed waves rather than endlessly, so a chamber is a fight you can pace.
Finding one
Chambers generate in most Overworld biomes but avoid the deep dark, so tunnelling at diamond depth will eventually run one over. Two faster methods:
- Follow the copper. Chambers are built from tuff, tuff bricks and copper, none of which generates naturally in a cave wall. A block of chiseled tuff or a copper bulb in a cave ceiling means you are already inside one.
- Mine at Y=-20 in a straight line. Chambers are large — often 100 blocks across — so a long horizontal tunnel finds one much faster than a vertical shaft does. The habits in how to mine safely still apply; chambers are riddled with dispenser traps.
Bring what you would bring to a fight, not to a mine: a shield, a Steak stack, and armour you would not mind scratching.
Trial spawners
A trial spawner looks like an ordinary spawner cast in copper. When you walk into its room it wakes up and releases a fixed wave of mobs, scaled to how many players are present — one player gets a smaller wave than four. When the wave is dead the spawner ejects its rewards, goes inert, and enters a cooldown of about half an hour before it can be used again.
That is the design decision that makes chambers repeatable but not farmable. You cannot AFK a trial spawner into a mob farm; you also cannot exhaust a chamber permanently.
The mobs are the ordinary Overworld roster plus two of 1.21's own: the breeze, which lobs wind charges that deal a single point of damage and throw you into whatever else the room contains, and the bogged, a mossy skeleton firing arrows of Poison. Both are covered with the rest of the roster in how to fight every hostile mob.
Cleared spawners drop trial keys, and trial keys are the point.
Vaults
A vault is a locked copper block with an item visible inside it. Hold a trial key and use the vault, and it hands out loot — diamonds, emeralds, enchanted books, wind charges, the Bolt armour trim, and the two trial chamber music discs.
Two things about vaults that trip people up:
- Loot is per player. Each player can open a given vault exactly once. In multiplayer everyone gets their own pull from the same block, and no one can strip a chamber before the others arrive.
- A vault is not a chest. It cannot be broken, moved, or emptied a second time. If you have already opened it, the vault stays visibly locked for you forever.
Going ominous, which is the only way to a heavy core
An ordinary vault will never give you a heavy core. For that you need an ominous vault, and for that you need Trial Omen.
The chain runs:
- Kill a raid captain — the pillager carrying an ominous banner, found at pillager outposts and leading raid waves. Since 1.21 it drops an Ominous Bottle instead of applying Bad Omen directly.
- Drink the bottle inside a trial chamber. Bad Omen inside a chamber becomes Trial Omen rather than a raid.
- Every trial spawner in range becomes an ominous trial spawner: bigger waves, mobs carrying the 1.21 potion effects, and a much harder fight.
- Clearing an ominous spawner drops ominous trial keys, which open ominous vaults.
Ominous vaults carry the Flow armour trim, better enchanted books, and the heavy core. The heavy core is not guaranteed — it is a roll on the ominous vault table — so expect several ominous runs before one appears.
Do not drink the bottle in the entrance corridor and then walk off. Trial Omen has a duration, and it is spent whether you are fighting or not.
Making the mace
The recipe is two items:
| Ingredient | Where it comes from |
|---|---|
| Heavy core | Ominous vaults in a trial chamber, and nowhere else |
| Breeze rod | Dropped by a breeze, which spawns only from trial spawners |
Both ingredients are chamber-exclusive, which is why the mace is effectively a trophy for finishing the structure properly rather than something you stumble into.
What the mace actually does
Swung on the ground the mace is unremarkable — 6 attack damage and a slow swing, worse in ordinary combat than a diamond sword. Its entire value is the smash attack.
If you are falling when you hit something, the mace adds damage based on how far you have fallen:
| Blocks fallen | Bonus damage added |
|---|---|
| First 3 blocks | +4 each |
| Blocks 4 to 8 | +2 each |
| Every block beyond 8 | +1 each |
So a 3-block drop lands for 18, an 8-block drop for 28, and a 20-block drop for 40 — more than a fully enchanted netherite sword does in a single hit, against a target that cannot be healed back up in time.
Two more properties matter as much as the number:
- Your fall damage is cancelled when the smash connects. You take nothing for the drop.
- The impact throws nearby mobs back, which clears the space around you before the next swing.
The mace has 500 durability and is repaired with breeze rods.
Enchanting it
The mace has three enchantments of its own, none of them available at an enchanting table — they come from chamber loot and enchanted books:
- Density V — adds 0.5 damage per block fallen per level, so 2.5 per block at level V. This is the damage enchantment.
- Breach IV — ignores 60% of the target's armour. Worth it against armoured players, wasted on most mobs.
- Wind Burst III — bounces you back up after a smash so you can chain one drop into the next.
Density and Breach are mutually exclusive with each other; Wind Burst conflicts with neither, so a finished mace is Density V, Wind Burst III, Unbreaking III and Mending. The anvil ordering that gets you there for the fewest levels is worked through in anvil mechanics and the "too expensive" limit.
Is the mace worth the trip?
For fighting mobs on flat ground, no — keep a sword. For anything you can get above, yes, and there is nothing else in the game like it: bosses you can pillar over, players in the open, and any fight where you control the vertical.
The honest reason to run trial chambers, though, is everything else: diamonds, enchanted books and armour trims at a risk level far below an ancient city. See every structure and its loot for how it ranks against the rest.
Frequently asked questions
Can I farm trial spawners for loot?
No, and that is deliberate. A spawner produces one wave, ejects its rewards, then sits on a cooldown of roughly half an hour. You can revisit a chamber as often as you like, but you cannot build a machine around one.
Do I need a key for every vault?
Yes — one trial key per vault, and ominous vaults need ominous trial keys specifically. Ordinary keys will not open them.
Can two players loot the same vault?
Yes. Vault loot is tracked per player, so every player gets one pull from each vault. Nobody can clear a chamber out from under anyone else.
Where else can I get a heavy core?
Nowhere. Ominous vaults in trial chambers are the only source in the game, which means the mace cannot be obtained without going ominous at least once.
Does the mace work with Sharpness or Smite?
Sharpness, no — the mace is not tagged as a sword, so the enchantment cannot go on it at all. Smite does apply, but it is mutually exclusive with Density, and Density is almost always the better pick. Plan the mace around Density, Breach and Wind Burst rather than around sword enchantments — the smash scaling dwarfs anything a flat damage bonus adds.
