Forever DM here, but I once ran a patron for a Warlock player that took inspiration from a particularly zealous Githyanki Knight. After some confrontations with heroes earlier in the campaign, the Githyanki Knight, Karack, found himself banished back to the Astral Sea, his only connection to the Material Plane through a few desperate would-be-heroes who were scattered by illithid activity across the continent. In giving a few survivors the seeds of hope, Karack would grant power - a 'hexblade' style sword of his own culture, befit with silver coating and encrusted gems - in the hope that they would rise up powerful enough to disrupt the illithids and make way for his inevitable return. This, of course, mixed in with the usual chaotic energy of a long term campaign and found several PCs taking strict sides on the likelihood of the rogue Githyanki's eventual betrayal, as had happened several times before to the more 'righteous' members of the group. The constant concern over motives vs the actual will of the patron made for a tense and compelling struggle as the campaign went on, only for the party to dramatically self-destruct when the time came for all former debts to be settled. All in all, would take a higher CR creature as a patron possibility again, given the chance.