Does the Illuminati worship Satan

No. Because if they did, at least one person chosen by them to initiate over the entire time the society has existed would be so horrified that they would not initiate and run tell all their secrets. Being said, that doesn't mean they don't center ritual on death and macabre, but all-in-all, it's just a boys club that thinks skulls and secrets are cool; it's the same thing kids in treehouses come up with, it's just this club is at Yale where all the rich and powerful are so it gets more notice.