So what now?
My guys are level 53-56 and have nowhere to train, since I don't have a pass to Olympus and no idea where to look for it.
Dungeon of Death?
Dragon Cave?
Isle of Illusions? Not tempting, since I hate those Minotaurs.
Explore more of outdoor Darkside? I've done all the towers.
Alamar's basement?
And how do I access that small area in the south west part of the sewers under Necropolis? Neither Etherialize nor Teleport works.
the pass? you get that from the Dragon Paraoh, after you investigate the second crash site and report back.
You won't be able to train again before you manage to handle those lovely minotaurs and their gorgon friends. They have to be defeated even in a MM5 only game so you should be able to do so with all the benefits you gained from MM4.
I explored the Dragon Cave, part of the dungeon of Castle Alamar, and the remaining part of the Darkside outdoors, and then did the Isle of the Lost (not Illusions, as I wrote). After gaining some levels and better equipment the Minotaurs weren't so scary anymore, but the Gorgons managed to get in a few stoning attacks.
Now my guys are level 61 and are ready to free Queen Kalindra from Castle Blackfang.
I haven't found keys to Dragon Tower, Darkstone Tower or the Southern Sphinx yet, so unless I've missed something (AFAIK the only thing I skipped were the Drawkcab monks since I really didn't know the word "palindrome") the end game is larger than I thought.