Unlike Kharne, I'm intending to have a detailed story line from the start with Stygia. This will manifest itself in many ways throughout the game, from factions the character can join, perform quests and obtain reputation for, to NPCs from different factions fighting each other if the character's actions have caused a war between them. I think C# will allow me to make a really good living world and NPC/Monster AI.
I've found two posts on creature AI in roguelike that I can't recomnend heavily enough: here and here. Certainly the first one (and its followups), courtesy of the ever informative Andrew Doull should be read by any budding roguelike developer.
Meanwhile, a random screenshot from the intro section (which I eventually hope to animate and sort out suitable music to accompany it) explaining the back story of the game: