The Thorium Mod adds 4 new variants of Mimics to the game, each having a corresponding biome.
The Thorium mod adds one new normal variant to the game. Normal mimics can only be found in their corresponding biome. They will look like normal chests until approached or attacked, at which point they will chase the player. The appearance of the mimic depends on the chests normally found in that biome.
The Thorium Mod adds three new special Mimic variants to the game. They have much higher health than normal Mimics, and a separate set of unique drops. They will spawn in their corresponding biomes, but unlike normal Mimics, they can also be summoned with the corresponding Key.
They attack by jumping towards the player, but they also have the ability to shut themselves, making themselves invincible. In the closed, invincible state, these mimics are capable of reflecting player projectiles. They can also perform a pound-like attack, where the Mimic jumps over the player's head and swiftly drops down; during this attack they can move through blocks. They can additionally dash rapidly after the player at high speeds (slightly over 51mph) if the player attempts to escape, and can sometimes dash through blocks.
- The Hell Bringer Mimic does not have an extended tongue like the rest of the Biome Mimics.