Dig into the mountain, collect resources to build your fortress, grow your population and keep them alive (and happy), learn new deadly skills, gather and refine materials to craft powerful items so you can fend off the many dangerous monsters threatening your colony in turn-based tactical combat.
Infested Fortress is a rogue-like with underground base building and tactical combat in a dark fantasy setting. You manage the colony as well as a (hopefully) growing group of heroes who must both keep the colony running and fight the battles.
You'll build up your infrastructure, learn new deadly skills, keep morale up, dig deeper into the dungeon to collect materials to make better and better equipment. You'll need this to survive against the many different enemies in a turn-based battle that is decided only by tactical skill and not by dice rolls.