Bloodlust is an ability believed to be utilized by the Claw of Shar.
Carefully harnessing the nether about the body, an assassin can allow the tendrils to feed upon their very blood to energize it into a frenzy.
These energized tendrils then allow the caster to move with unnatural speed and precision. Only those very skilled with sorcery can manage to control such dangerous power. The speed comes at a high cost to the body, and can be risky as the effect cannot be easily undone.