Bloodline of Adramelech

Adramelech,  The so-called Sunking and many other pompous titles besides. He is the patron of many a power hungry wizard and warlock, and he gives his power away willingly, for he knows that any who takes his offer is forever damned, returning to him in death. This way he gains back all the power he gave away and everything the mage accumulated during his life. Thus he gains power on the suffering of others. The spawn of Adramelech are the most outwardly monstrous of the bunch, most of them barely humanoid in appearance, yet they are magically the most powerful. Unnatural pyrotechnics flow from the hands of these beings, overwhelming their foes with infernal sorcery. Tieflings of this bloodline are the most reviled, and most common to seek the darker path.

-Chemardale, The Red Prince

Bloodline of Adramelech:
ASI: +4 to Int
Sunking's Spawn: You know a number of Wizard spells equal to your proficiency bonus. You can swap these spells for other ones on a short or long rest. You can cast these spells a pooled number of times equal to your proficiency bonus. Spells over the 4th level take 2 slots, spells over 7th take 3.