Warlocks patrons are often powerful beings, a great source of inspiration when you homebrew subclasses. Pick any powerful being and make them into a patron. In addition, Warlock’s usual template is simple. 1st level is a feature often offensive used to spread your patron’s influence, 6th level is a defensive reactive feature and 10th level is an aspect of the patron that the Warlock make theirs to protect themselves. And then the capstone, at 14th level, is a powerful feature that makes you go “woah”. And so I picked one of the most iconic powerful being of D&D, the Beholder.
Invade the Material Plane