I mention this because I'm looking for feedback. Not just from the players, but the community. Was it the pacing good? Bad? Sending the party's wizard into a temper-tantrum is never a good sign. What about the NPCs? Marley was supposed to be respected and feared, but overall likeable. Was this achieved? Was Marley going "super saiyan" too cliche?
Honestly, I thought Marley comes off as too perfect. He's a powerful crime lord, but he's honourable, rich, powerful, has a good sense of humour, isn't phased by any of the weirdness we spout, and is clearly a hero. It seemed like the only reason he wasn't solving everything himself was that he was too busy doing other things, which isn't a great way to make the players feel important.
So then coming back and finding him apparently dead was brilliant! "Oops, that super-powerful guy who's more heroic than you got his ass kicked! Guess it's all up to you now, good luck!" I really felt like we were in for a good fight for a while there! (Even when he turned out to be alive again, it didn't take away from that, because the bad guys were still powerful enough to disable and capture him, and the focus was still on us.)
Then when he busted out - I didn't like that much at all. Takes too much of the focus away from the heroes. Focusing on just one enemy and letting us take on the rest is a pretty good way to handle this, but I would have preferred it if he'd stayed incapacitated until the end of the fight.
I had the same problem in a game I DM'd last week, actually. I'd set up two powerful rivals and statted them both out as end bosses, with the idea that the players would side with one of them and fight the other one - but the way it went down, they ended up fighting one with the other one present and I couldn't think of a good reason he wouldn't join the fight on their side. And because he was supposed to be an end boss, he was about as powerful as the entire party together, and toning him down would have led to questions about why his rival didn't just kick his ass long ago... I ended up having him get a few good hits in before the rival hit him with a mind-trapping illusion spell (which I'd made up on the spot) that took him out of the fight entirely and let him focus on the players.
So, to summarize: characters that outclass the playes are best kept mostly off-screen, IMHO, or used as backgrounds. (Fighting powerful enemies around the feet of an angel battling a titan = cool, since the players are SO outclassed that they're beneath their notice so they're more like scenery, like a volcano erupting, than actual characters. Once the characters are at a scale where they could be considered legitimate rivals to the players, but still clearly outclassing them, they start to steal the spotlight.)
The only other criticism I have of the adventure is that the answer to what happened to Marley was pretty much handed to us. I'd have liked a bit of investigation instead of just being led to the next location. (But I guess then it would have been hard to justify that the ritual wasn't over by the time we got there, so maybe it was better this way. I guess a good medium would have been to find some token that Ash would recognize as belonging to Hyann or coming from that specific warehouse, instead of having an NPC blurt out, "It must have been Hyann, and here's where to find him!" I found that pretty unconvincing.)
Other than that, the adventure was great, and 7 Rabbit is definitely very interested in getting in on the sequel (especially if it involves learning more about the nature of spellcasting...) It goes without saying that the echoes were awesome. I thought the number of things Marley's echo was able to do at once was a little ridiculous at first, but it turned out to be a really good fight (and my own tries to create solo's always fizzle, so I think you have a better handle on how much they should be able to do than I do).