How to get Under Lock and Key advancement in Minecraft

The seven new advancements in Minecraft are some of the less discussed additions in the 1.21 update. These are often introduced with the aim of encouraging players to explore and engage with the new features introduced in the update. As a result, new advancements are typically closely related to these new features, incentivizing players to try them out.

In the 1.21 update, one of the seven new advancements introduced is Under Lock and Key. In this article, we will explain how to complete the Under Lock and Key advancement in Minecraft, providing some tips to help you accomplish it efficiently.

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Guide to get Under Lock and Key advancement in Minecraft

Under Lock and Key advancement's description in Minecraft (Image via Mojang)

The Under Lock and Key advancement in Minecraft can be completed by unlocking a vault with a trial key. The vault is a block that ejects various items upon being unlocked, but obtaining a trial key can be a bit of work. Vaults can only be found in trial chambers, an underground structure generated exclusively in the Overworld.

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How to locate a trial chamber

Trial chambers explorer map (Image via Mojang)

Since they are underground structures, it is challenging to discover trial chambers while exploring the world of Minecraft. However, the game offers a trial chambers explorer map that leads players directly to the nearest chamber.

Once players reach the trial chamber symbol on the map, they should dig downwards until they reach approximately Y level -20. This depth is where the structure of the trial chamber begins generating.

To obtain this map, players must trade with a journeyman-level cartographer. Once inside a trial chamber, coming across vaults is relatively easy, as a considerable number of them spawn within the structure.

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How to get and use trial keys

Completing the Under Lock and Key advancement in Minecraft (Image via Mojang)

Trial keys are rare and primarily sourced from trial spawner blocks. After a player defeats all the mobs spawned from a trial spawner, the block has a 50% chance of ejecting a trial key as a reward. Each trial spawner can summon up to six mobs when a player is nearby, with an additional two mobs spawning for each extra player in range.

Breeze spawners operate differently, summoning two breeze mobs initially when a player is around and an additional one for each extra player present. Once all the mobs have been defeated, the block will reward the player and then go on a 30-minute cooldown.

To use the key, players need to left-click on a vault with the key equipped, and upon doing so, the Under Lock and Key advancement will be completed.