Sentry

This is a Sentry

Sentries are slime-like mobs spawned in the Bronze Dungeon upon stepping on a Trap Block. They are a gray color with blue eyelike symbols on their front sides. Trap Blocks look exactly the same as regular Dungeon stones. Even changing your texture pack will not make them more distinct, as the game engine forces both blocks to use the same texture.

Sentries will jump towards you, similarly to slimes, and will explode, dealing 1.5 hearts of damage with no armor on, and significant knockback upon touching you. They take damage from any source. Upon being killed, they will drop Carved Stone (which is also obtainable from killing the Slider) or Sentry Stone.