While the first Dungeon Defenders game was quite a good action-RPG game, Trendy Entertainment just announced a sequel that will go down the free-to-play route.
Dungeon Defenders 2 is expected to include a co-op mode just like in the original game but with more heroes (24 playable characters at launch), loot and towers, while another mode will be competitive, taking the format of a MOBA. This last mode is already available in a closed beta to some lucky players. If you wish to try your luck you just have to sign up here: http://dungeondefenders2.com/blog/
Dungeon Defenders 2 is in development for PC, Mac, iOS, Android and Web, with cross-platform already announced.