"The Mule" is actually Gigantico the music bald guy, and The Mule we see is basically his meat puppet he uses as a front. I'm not sure if they are brothers or maybe the Mule's backstory was partially true and the first warlord he ran across, he "took over" and made a front for his galactic conquest.
Second foundation seems kinda lame right now, Gaal is ok (she is nowhere as terrible as the previous strong black womyn) but her, the deaf guy, and Han NotSolo are a pretty shitty team to go up against Foundation/Empire/Mule. I wish they had a stronger, dominant male character there to be the Mule's foil.
Seems like Dusk is gonna deploy the death star (Asimov would have hated that lol) against Trantor, and our heroes are gonna be caught up in the event horizon or something. Still a lot of questions on who exactly is this god-like being that revived Seldon (spacers from the future?), what is Demezerel gonna do if Empire dies off, and how the Prime Radiant even really works. It all feels like magic.