Requirement: being able to cast 3rd level arcane spells as per description.
Pale Master increases caster level by 1 at each odd level (as per wizard's spell level progression) and also provide new spells to sorcerer/bard
after becoming the Pale Master, character's alignment is locked to Evil. Character with levels in PM won't be able to change their alignment on a good/evil axis, only on chaotic/lawful axis.
Can't take epic spells, unless you can cast 9.level spells. (19int/wisdom + spellcasting class with 9.level spells)