The gameplay is primarily action-oriented. Numerous enemies attack the player in waves, and progress to the next part of the stage often requires defeat of all enemies in the area. The main feature that lends originality to the series is the addition of the Chaos Legion, which are supernatural creatures that fight alongside the player.

While Legion are summoned, Sieg Wahrheit (the player character) is unable to run and has weaker melee attacks. Legion can be controlled to a degree: their tactics can be switched between offensive and defensive, and players can issue orders for them to attack immediately. While the Legion are inactive, Sieg can perform a sort of “special attack” called an Assist Attack which causes a Legion to appear and attack with him.