This is the cast type skill for chaos spells.
The in game help reads:
Skill duration: random. Type of skill : spell casting skill (arcane skill). Affecting stats: None. It uses no endurance points. The followers of chaos have long had their own tricks for making magic happen. While other disciplines generally rely on strictly set patterns and methods for harnessing the natural powers, chaos casters rely on doing everything, at the same time. A chaotic magic user casting spells is a sight to behold - first, one laughs, then one cries, then - permanent silence.