In the campaign world I am creating, spirits are a big part of magic. Clerics and druids essentially ask spirits to perform tasks for them. Wizards ignore spirits and manipulate magic directly, which is why they can cast any spell they so desire regardless of alignment but also have a theme of having to work and study quite hard for just a little spark of magic. Sorcerers have a spirit patron that is bound to them from birth, giving them the powers of a wizard with the ease of a cleric.
In this campaign, familiars are the manifestations of those patrons, and so wizards do not have them. Instead, wizards may use the animal companion variant or any of the specialist wizard variants in the SRD. BUT I want to give wizards a chance to acquire a spirit patron by making a contract with an evil spirit, which increases their power, but at a price. my first instinct was to make this a feat, but it might become a prestige class a la tainted sorcerer.Soul-Sold
You have made a pact with one of the Fallen, offering your soul for greater power.Prerequisite:
Wizard Level 5th, Corrupt Spell.Benefit:
You obtain a familiar as a sorcerer, except this familiar has the fiendish template. In addition, When you cast an evil spell with your fiendish familiar in arm's reach, your wizard caster level is considered two points higher. However, should you perish, you cannot be raised or resurrected by any means. You are also considered to have the evil subtype in all situations in which it is harmful to you.
Is it too imbalanced? If so, how might I improve it?