Infernal Affairs

Arcane devotees known as Warlocks gain their power not from the arcane energy of their surroundings, but from making pacts with otherworldly entities.
Often times, fledgling Warlocks will reach out to powerful devils, or the other way around. These pacts are known as Infernal Pacts, and some say they allow a Warlock to wield the most powerful forms of arcane energy. However, these pacts often come at a price, as devils are known to be shrewd bargainers. While some lesser devils may ask for special favors to help them vie for power in their home realms in the Nine Hells, the more powerful fiends will often require a steeper price. This could come in the form of the Warlock pledging their soul to the devil, redeemable upon death.
However, contrary to what most people believe, forming a pact with a fiend is not always an evil act, nor do fiends only seek out pacts with evil Warlocks. For instance, it is not uncommon for an archdevil, such as Belial, to seek out and forge a pact with a heroic Warlock in an effort to eradicate the stigma associated with Infernal Pacts. Smart devils know that the more Warlocks feel comfortable making such pacts, the more it will benefit them in the end when it comes time to collect.