This is the cast type skill for control 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. One family of magic that is as old as magic itself, are spells that are woven that break the very limits of nature and its laws. Magical spells that enhance abilites beyond normal physical limits, and that defy other natural limits, are part of this type of magic. To cast these spells effectively, one must learn what makes up the laws that determine what natural limits are, and how to supercede them.