OK, so I've taken a break from puzzles to actually play through a few class challenges, and... wow.
Amazing work from you guys here. Magician is a blast to play - feels very powerful, and finally makes Elves feel good to play (I've always seen elves as overshadowed by gnomes in every way because there are so many ways to increase your mana, so this is really something!).
I blew through the bronze challenge on my second try (not my first try because I didn't read the rules

), then beat Silver on my first try with the Earthmother. The silver challenge was very cool, and I especially like how strong the Magician is with the Earthmother - the synergy with Entanglement + the extra glyph to convert seems like a really solid combo. EM has always seemed a tad weak to me, mostly because of the random plants easily screwing you, but with this class it's more than worth the risk (and also he has WEYTWUT so even if you get blocked off, you can escape!).
Looking back, Magician Silver would have been a LOT easier if I'd used the barrels of weasels, but I barely even needed them. The Bag o' Tricks itself looks like a pretty good item - kind of similar to Dragon Soul, in a sense, with the RNG element. It's kind of like Namtar's Ward in the sense that it's more of a standalone item that doesn't need to stack with anything else to be good. Especially since you can see what your next free cast will be, it's an insanely powerful item. The only thing I'm sad about is that you can't refill it.

After that, I scouted Magician Gold and decided not to try it just yet - I want to play around with the class a bit more and get to know it in normal gameplay, first. Instead, I've started on the Heretic.
Heretic Bronze was pretty interesting - it gave me an actual "role-playing" sense and made me actually invested in the story, similarly to playing through the triple quests for the first time, or the Vicious dungeons.
As for the gameplay for Heretic Bronze, that was probably the only part that bothered me - I would kill the level 10 goat, get the artifact, feed it 30 piety, break the scriptures, feed it more piety, and then realize I didn't have enough monsters left to level up again (I overleveled before fighting the goat, probably.) As I understand it, you're required to level up in order to smash the altar and fight the boss, so I was basically softlocked (and to add insult to injury, the game won't let you retire, either, so I had to restart from the menu). I would suggest having some kind of infinite source of EXP somewhere (maybe, every time you kill an undead, the boss spawns one on the floor?) so that you can't run into this problem. Aside from that though, a very cool challenge.
I'll check back in later with more feedback!