Trial spawners are found exclusively inside trial chamber structures introduced in Java and Bedrock editions. Unlike normal spawners, they detect all players within a 14-block radius and scale the number of simultaneous mobs by player count — a solo player might face three mobs while a group of four faces twelve.

Once all active mobs are defeated, the trial spawner opens an adjacent vault and enters a cooldown phase before reactivating. Each player receives loot from that vault once per in-game day, making group runs significantly more rewarding. The loot pool contains ominous trial keys, emeralds, iron equipment, and rare enchanted books.

When a player carrying the Bad Omen effect enters a trial chamber, every trial spawner in range converts to its ominous variant: darker particles appear, spawned mobs carry enchanted gear and throw potions, and the associated vault offers rarer rewards. Trial spawners cannot be mined or moved — they drop nothing even with Silk Touch — preserving the challenge structure of every chamber.