OpenDungeons is a nice open source game strongly inspired by the Dungeon Keeper series and its legacy. The game is actively developed by an international team of developers and artists, so grab it on http://opendungeons.github.io, give your feedback and why not get involved in future releases!
This tutorial aims at explaining the basic gameplay concepts that you need to know to play OpenDungeons 0.5.0, which lacks an in-game tutorial. Hope you won't mind the thick French accent ;-)