At its heart, Ninety-Nine Nights II is a vast combat title, with hundreds of enemy creatures on screen simultaneously. As the camera picks over the action, the player can use a wealth of easily-effected combo attacks to carve a path through the enemy, and also use whatever weapons and items come to hand. At the end of each skirmish, players will then face a Titanic Boss Battle against the champion of their current adversary, with players forced to move quickly and locate the well hidden weak spots of these seemingly unstoppable behemoths.

Ninety-Nine Nights II also has a stunning two-player co-op online mode, where players team up against the oncoming hordes, working together to expand their combo range to take out more enemy assailants at once. This two-player mode features online ranking boards detailing the most effective pairings across the globe.