I really enjoyed this map. Big fan of the setting and the dungeon crawling aspects. All the different environments meshed together as an organic whole and the lighting was lovely. Combat on Nightmare/evil difficulty was sufficiently brutal and claustrophobic. You're really fighting for space in the initial stages of the map with very good use of elevated crossbow archers and ogres to complicate matters. Ambushes, traps and environmental hazards combined with the somewhat limited health and armour give the map a hostile and oppressive atmosphere that doesn't let up.
The final fight is great fun and to go against the grain somewhat, I actually appreciated how awkward and cramped it was to navigate. You're given the opportunity to inspect the arena before triggering the battle and the placement of the inactive stone knights gives a very good idea as to what is going to happen, so an observant player can choose to smash the pots and clear a path for when it all kicks off. You have to be deliberate with any rocket shots to avoid self damage and decide when to switch back to the widowmaker. There's a nice tension between wanting to clear out the big flail wielding knights quickly with the rocket launcher and fearing a stone knight suddenly blocking a rocket at point blank.
The one weakness for me is that the secrets are probably too powerful: The early blast belt is extremely strong because it negates the damage from the gargoyle projectiles in the outer courtyard, allows for some aggressive skips and mitigates a lot of the risk from self-damage in the final arena. Similarly, the platforming section in the crypt is very tense and precarious in normal play, but the entire section can be bypassed with the secret enviro-suit at the start. There seems to be a secret for every major obstacle that really lets you overcome it without any strings attached. Personally, I prefer it when there's some sort of adverse reaction or cost involved with grabbing a high value powerup. That, or a need to think carefully about when and how best to use it.
I was also surprised that there was no payoff or acknowledgment after killing the boss in the secret area, though the fight itself was reward in itself and well worth the effort in finding. The guy just seems to be hanging out there for no real reason.
Quibbles aside, this was a lovely map. You've made a great map for copper, alkaline and now AD. I'm looking forward to future releases.