Heroes and Castles is the latest game from the guys at Foursaken Media (who, I believe, I first met up with at Macworld around this time last year). It's a little bit more involved than anything else I've seen them do -- on the surface, I'd probably compare it most to the great Dungeon Defenders, a really excellent game on iOS or Steam that you should check out if you haven't yet.
Heroes and Castles isn't quite as well-polished as Dungeon Defenders, but it is a lot of fun. It's a third-person action game, where you play as a fantasy character either hacking and slashing or casting spells against oncoming waves of baddies. But the twist here is that it's also a tower defense game: In addition to your own attacks, you can also buy an army to help you fight off enemies, or buy repairs and defenses for the town you're protecting. There's a lot of depth here: In addition to three different player classes, there are lots and lots of various units and defenses to unlock as you play along.
Heroes and Castles isn't a perfect game -- the graphics leave a little something to be desired at times (though they also shine in the right places), and the touchscreen controls are a little too simple for a game that is as deep as this one. That camera, especially, is sometimes tough to turn around, especially when you need to see where your wall is being attacked on a moment's notice. But for US$1.99, Heroes and Castles is a great bargain of a game -- it's the most impressive outing I've seen from Foursaken yet, and it's a great action/RPG/defense title that's well worth the purchase.