A Fury.
A Fury can be summoned with the Level 16 Sorcery power Summon Fury.
A Grand Fury, along with a Grand Watcher and a Grand Guardian, may be summoned with the Grand Summoning power.
Trivia
- The Fury used to resemble a burning skull with horns, but this was later changed into a small, robed humanoid. This also removed any visual differences between the Fury and the Grand Fury (which used to burn green and red respectively).