A Stone Grimace is an invincible stationary statue of a head, with a wide open mouth and hollow eyes.
They will sporadically spit a red bullet at Isaac's direction until the room is cleared from regular enemies, although they will sometimes attack 1 extra time after all the enemies are defeated.
Although indestructible, tear effects will still affect them, so it is possible to decrease their shot speed with Spider's Bite, or their range with items like Little Gish. It is also possible to petrify them briefly with Mom's Contacts.
They are considered regular monsters by Attack Flies or familiars like the Dead Bird, which might end up attacking one even though this will have no effect.
They cannot be passed over with Flight.
- It's possible to encounter an eternal champion in original Binding of Isaac, however this only happens after you've cleared the room, which means it will never shoots, therefore it's impossible to know its bullet pattern. This also applies to Slide.
- Stone Grimaces could be a reference to the statues in the original Legend of Zelda, which are also stationary, indestructible and shoot fireballs into the player's direction.