Dungeon Warfare is a challenging tower defense strategy game where you become a dungeon lord to defend your dungeons with deadiest of traps and insidious contraptions against greedy adventurers and wanna-be heroes.
This is one of my favorite TD games. They're still in Alpha 16, but everything seems to be finished, aside from the last battle.
The game plays a bit like an isometric Tecmo's Deception, except on a larger scale and with automatic traps. There are somewhere around 30 missions and you can select your own challenges for increased XP to add replay value to completed missions.
A great tower defense game. Dungeon keeper meets the tower defense genre. Currently the game is in early release. The developer has been making steady progress on it and has been adding new features on a somewhat regular basis. Even in its unfinished state it is a solid game. The only thing I'd like to see are more levels.