From Guild Wars 2 Wiki
Fractal Avengers are special NPCs that only appear in Fractals of the Mists at difficulty scale 70 or higher. Whenever a player gets downed during the fractal, an avenger will spawn on top of their body and attempt to finish them.
- Finishes players.
- The avenger's finisher will fizzle if its target moves out of range (e.g., Deception, shadow Escape, Vapor Form) or enters stealth.
- Players can disable or kill the avenger while it's channeling to interrupt the finisher.
- Avengers will not attempt to stomp again if they are interrupted too early.
- Avengers will be destroyed instantly when interrupted or after stomping a player.
- Avengers will only be able to stomp the player for which they spawned.
- Other hostile NPCs in the fractal will attempt to attack and kill avengers.