Eldritch magic is a powerful, primal version of magic with a violet blue to dark purple coloration. Eldritch magic is thought to serve as the foundation to both arcane and divine magics. The only real proof stemming from this conjecture is that both arcane and divine spellcasters are equally affected by the lure of Eldritch Magic. Standing in the presence of Eldritch magic treats the caster as if he had an infinite number of hero points to spend in the augmentation and creation of spells.
Any serious study of Eldritch magic is in the hands of seriously mad men. There are however a few known constants about Eldritch magic and its effects. Eldritch magic appears to accelerate the mental corruption in spellcasters, while decelerating their physical corruption. If prolonged exposure didn’t cause insanity, one might even say that Eldritch magic is healthy for arcane spellcasters in particular.