ADOM is a fantastic fantasy roguelike game by Thomas Biskup. Lineage wise, it's technically a Hack-like, I think, but it's so different to Nethack that it's barely recognisable and plays much more like a classic fantasy CRPG.

ADOM has complex mechanics and an old school design, and is quite unique amongst the so-called "major roguelikes" in that it bears the marks of the developer's personality.

I think it's excellent, and I hope you enjoy it too!