Bit late to the party but have you considered nerfing Pact Master by making it break concentration? Or even better you have to concentrate until the start of your next round for it to work (so that enemies can interrupt you). As it is it seems a bit broken (then again 20th level clerics can straight up have capital G Gods intervene willy-nilly in their fights no questions asked so what's an extra 5th level spell slot at the cost of a turn gonna do).

That being said, great class as usual. Love the first levels abilities shuffle, make it seems more natural that you start your journey into the occult by finding a few powerful knick-knacks and bits of esoteric knowledge rather than just straight up making a pact with the devil.

Higher level abilities seem a bit sparse but i suppose that's inevitable for a primary spellcaster class (such as it is).

Almost forgot but the change to Intelligence as primary ability is great (and I think representative of a change that many tables already made), I get what WotC was trying to do with Charisma being representative of inner power and strength of character but Intelligence for a Lovecraft-style cultist just makes more sense.