It's ADOM for me, first Roguelike I really got into.
I found TOME one fateful day and decided to try it, I think I'd read an article about roguelikes and as it covered the various games, I saw noted "There's also TOME, but I don't think many of us are *that* hard"
So naturally, I had to try it

*blames being Scottish*
Mind you, ADOM wasn't listed in that article, and I'd certainly say that was harder, no methods of recall that I remember, very hard to learn to teleport as a non-mage (or mage even), curses are a git to remove, traps very often destroy items completely and means of healing (potions) are scarce in the early game. Oh, and it's generally considered impossible to win without gaining around half a dozen corruptions, only been a few exceptions AFAIK.
Gets easier when you learn a few tricks, but I like TOME a lot better, despite how many, many differences there are. (maybe that's *why*, infact)
Elemos.
'You see a Forumite. It is a rare form of troll. It is normally found on TomeNet, and is immobile. It is magical, casting spells erratically which confuse, corrupt, cause cursing, and cause blindness; 1 time in 5.'