There are apparently two Gaan-Telets. The first one requires you to play purist, has a total of five floors (surface, three randomly selected floors filled with monsters, and then the bottom floor with a much weakened Horatio). The second one is just the top floor with a level 8 Horatio with the old stats, and since there are no deities the only real way to beat him is a swift hands assassin.
I'm actually kinda disappointed hard mode Gaan-Telet disappeared. If you took out the Illusion and Animated Armor levels, it was actually a great scenario and I wouldn't mind replaying it.
The floors I've encountered thus far are these:
3 animated armors and the pactmaker shrine
5 goblin miners (mana burn) and Binlor's shrine
5 goats and Taurog's shrine. After the first goat dies, all the goats get doable damage, turning them into mini-Bleaties.
4 Trolls and the Bridge Troll (Drops a sensation stone! This is a lucky find if you get it!)
several illusions (I just quit the moment I saw it, didn't even scout the level)
5 snakes and a shrine (forget which one)
5 vampires and Dracul's shrine
5 red wraiths and Glowing Guardian's shrine
After getting some combination of a crash, animated armors, or illusions five times in a row (seriously >_<) I finally won with Goats->Goblins->Trolls, grabbing Parched and Faithless. Very luck-based level, but definitely hard and not vicious. I don't think I've ever made it through a vicious level parched...