Dungeon Defenders

Dungeon Defenders is a mix of tower defense, RPG, and high fantasy/action/adventure where one to four players work together to protect one or more Eternia Crystals from being destroyed by waves of enemies which include goblins, orcs, kobolds, ogres, and wyverns. The game features a number of levels, consisting of around five total waves, through its campaign mode, or other levels as part of challenges. (wikipedia.org)