The goal of Hero Defense is to prevent ceaseless waves of enemies from reaching a certain end point (marked with, in giant letters, "END").
Waves will continue for several rounds until the player is greeted with "Final Wave!" after which, a score is calculated for each character playing the game. Players can quit via the pause menu after this time.
Players will spawn with 1,500 coins next to two vendors, both with a wide array of stock. Players begin with no keys and no ankhs, as there are no openable doors or respawn points of concern. All class abilities and offense upgrades are available from the start, beginning at tier one. Alongside the usual buyables one would expect from the campaign mode, there are also the following:
- Extended Path (Base price of 3,500): "Increases the distance enemies must go to reach the end."
- Fire Shooters (Base price of 2,500): "Increases damage and number of fire shooters." (Traps that cause monsters damage; base damage of 25, going to 200 at level 3. Highly recommend to complete the mode).
Note that monsters do not harm you in this game mode, so don't be afraid to approach them and attack as much as possible. Also, purchasing health or defense upgrades has no purpose.
Upon being slain, the monsters will drop their usual campaign drops: money (along with magic crystals). Players may collect the dropped money to purchase more items from the vendors throughout the game. It is also worth noting that once a monster reaches the end goal (and deals its 'damage' to the goal's health bar), it will take 10,000 damage and kill over, most likely leaving money behind.
If the player does not make it to the final round, this means defeat of the players, caused by the displayed health bar becoming completely empty, the splash text "Failure! You lose." will appear on the screen, the remainder of the enemies of the current wave will rush into the END goal, and the waves will cease. The players will then be forced to quit via pause menu to return to the main menu.