There are currently four available heroes in the game, with two more yet to be revealed or unlocked. Each hero have their own abilities and towers. In addition, they can also heal themselves. Each hero can deploy four types of towers/traps, and have four different active abilities. As heroes and their deployed towers defeat enemies, they earn experience to level up. Leveling up allows them to wear better gear and unlock more abilities and towers. Players can create multiple characters but they can only assign three of them in a Deck.
The Deck allows easy access to the selected heroes when you're managing their equipment via the Hero Manager feature in the tavern. The Heroes in your deck must be within the level range of the selected session. Heroes that don't meet the level requirements will be removed from the deck but you can add them later in the Hero Manager. Players can also strengthen their heroes through Specs. This is basically your character's skill tree. You'll earn Skill Points and use it to improve your listed Specs. The game also offers Respec which is basically resetting the your allocated points so you can re-assign them.