Eltab
Lord of the Hidden Layer
I like the idea 'my character has special training, and I have access to this special spell.' Keep the lists short, like Paladin Oath spells. The spells might do something unusual, like being an exception to the rule. (Fiendish Form: You gain the resistances common to fiends. You look fiendish. Runs out in 1 minute.) The spells might be from a 3e source. And be sure the special spells are not so much better than normal spells that every other spellcaster you meet would want to steal your copy for themselves.