Fenrir

Fenrir is a Hunter-class cat miniboss with 75 HP, 5 damage, 4 movement, and 5 Luck, found in The Alley. Named after the monstrous wolf of Norse mythology fated to slay Odin during Ragnarok, Fenrir is recognizable by his missing eye, a nod to Odin's own sacrifice of sight. Edmund McMillen has noted Fenrir as "the most infamous among playtesters" due to his disappearing bear traps. He represents one of four Alley minibosses, each corresponding to a different player class.

Fenrir's combat revolves around two abilities. His Lobbed Shot is a ranged attack that damages a unit up to 3 tiles away. More dangerously, he deploys Bear Traps at random positions 2 to 4 tiles from himself, which become invisible shortly after placement. Fenrir prioritizes setting traps over direct attacks, steadily mining the battlefield with hidden hazards. He also knocks back any melee attacker that strikes him, punishing aggressive close-range approaches. Fenrir gravitates toward tall grass tiles and moves away from allied units, using the terrain to hide and reposition.

Fire-based attacks are highly effective against Fenrir because burning grass tiles forces him to reposition and can even damage him when he moves through fire. Wind abilities can remove tall grass entirely, eliminating his preferred hiding spots. Hunter-class cats with the Marked ability can prevent his evasion in grass. Notably, Fenrir can walk into his own traps, which occasionally happens due to pathfinding quirks. As of patch 1.0.20736, physical attacks can trigger and safely disarm traps. Track trap locations using map landmarks, and use missing melee attacks strategically since failed hits do not trigger his knockback retaliation.