Dwarf Fortress. There aren't many mods in the steam version afaik (tons for the free ascii version though) but... You don't need mods for it. Want to capture invaders and host gladiator fights? Yep. Water trap to push invaders off a cliff onto some grates so you can collect their items after blocking the water trap again? Easy peasy floodgates Parcheesi. Want to gift lead mugs to the filthy elves? Strike the Earth, brother. (Doesn't poison them though, sadly). Want your dwarves to only drink alcohol? They only have to drink water when they're injured, 24/7 drinking besides that makes for happy dwarves. You're battling a bunch of invading goblins and you have some dwarves die? Better bury them or their ghost will haunt your fortress. Oh, and don't forget your necromancer will probably grab some new friends from the fight.

There's very little you can't do in Dwarf Fortress. It doesn't get very high tech since it's fantasy based, most high tech that you can get is windmill driven mills and water pumps I think, but there is so much depth to the game that honestly that's perfectly okay with me

Edit: there are mods for the steam version too, baked right into the steam workshop