You have made a pact with a fiend from the lower planes of existence, a being whose aims are evil, even if you strive against those aims. Such beings desire the corruption or destruction of all things, ultimately including you. Fiends powerful enough to forge a pact include demon lords such as Demogorgon, Orcus, Fraz’Urb-luu, and Baphomet; archdevils such as Asmodeus, Dispater, Mephistopheles, and Belial; pit fiends and balors that are especially mighty; and ultroloths and other lords of the yugoloths.

You have made a pact with one of the rarest kinds of genie, a noble genie. Such entities rule vast fiefs on the Elemental Planes and have great influence over lesser genies and elemental creatures. Noble genies are varied in their motivations, but most are arrogant and wield power that rivals that of lesser deities. They delight in turning the table on mortals, who often bind genies into servitude, and readily enter into pacts that expand their reach.

Your patron is a mysterious entity whose nature is utterly foreign to the fabric of reality. It might come from the Far Realm, the space beyond reality, or it could be one of the elder gods known only in legends. Its motives are incomprehensible to mortals, and its knowledge so immense and ancient that even the greatest libraries pale in comparison to the vast secrets it holds. The Great Old One might be unaware of your existence or entirely indifferent to you, but the secrets you have learned allow you to draw your magic from it.

Entities of this type include Ghaunadar, called That Which Lurks; Tharizdun, the Chained God; Dendar, the Night Serpent; Zargon, the Returner; Great Cthulhu; and other unfathomable beings.

You have made your pact with a mysterious entity from the Shadowfell – a force that manifests in sentient magic weapons carved from the stuff of shadow. The mighty sword Blackrazor is the most notable of these weapons, which have been spread across the multiverse over the ages. The shadowy force behind these weapons can offer power to warlocks who form pacts with it. Many hexblade warlocks create weapons that emulate those formed in the Shadowfell. Others forgo such arms, content to weave the dark magic of that plane into their spellcasting.

Because the Raven Queen is known to have forged the first of these weapons, many sages speculate that she and the force are one and that the weapons, along with hexblade warlocks, are tools she uses to manipulate events on the Material Plane to her inscrutable ends.

Death holds no sway over your patron, who has unlocked the secrets of everlasting life, although such a prize – like all power – comes at a price. Once mortal, the Undying has seen mortal lifetimes pass like the seasons, like the flicker of endless days and nights. It has the secrets of the ages to share, secrets of life and death. Beings of this sort include Vecna, Lord of the Hand and the Eye; the dread Iuz; the lich-queen Vol; the Undying Court of Aerenal; Vlaakith, lich-queen of the githyanki; and the deathless wizard Fistandantalus.

In the Realms, Undying patrons include Larloch the Shadow King, legendary master of Warlock’s Crypt, and Gilgeam, the God-King of Unther.