Quite a lot, as it turns out.
Overlord Tower Defense is, well... a tower defence game. It's also a cunning piece of marketing by Codemasters for all three of its new Overlord games.
There's not a lot to say, really, about yet another tower defence game. It uses the varying special abilities of Overlord's minions, so your brown dudes are your basic grunt, the red guys spit fire, etc. But essentially it plays like a tower defence game and it'll keep you playing all throughout the rest of this Friday afternoon.
And while you're at it, why not enter our competition to win Overlord II.
Overlord Tower Defense [Atari]