Mister Stabby is a Hardmodeenemy that only spawns during the Frost Legionevent. It chases the player and occasionally stops to do a considerably long stabbing animation with its knife. When attacking the player, it will dash and bounce around the terrain, making it difficult to hit it. Arguably, the best way to combat its speed and rapid bouncing is to use a spear or a decent ranged weapon.
Mister Stabby is the only snowman from the Frost Legion that does not have a visible smile on its face.
It appears to be holding its knife by the blade, instead of the handle.