Mister Stabby

Mister Stabby is an enemy in the Frost Legion. It chases the player through most terrain that it was encountered, and occasionally stops to do a considerably long stabbing animation. When attacking the player, he will dash and bounce around the terrain, making it difficult to hit him. Arguably, the best way to combat its speed and rapid bouncing is to use a spear or a spammable ranged weapon.

Mister Stabby is immune to the Poisoned, On Fire!, and Cursed Inferno debuffs.

Trivia

 * The name of this mob could be a reference to -ts stabby stabby, a famous competitive TF2 player who is widely regarded as the best spy of all time.
 * Judging from the location of the cross-guard (the part above the grip), it looks as though it is actually holding the knife by the blade instead of the grip.