Mortuus is a round-based zombies FPS for 1 to 4 players, played solo or in online co-op. Every run builds a new procedurally generated brutalist map, so the doors, perk machines, mystery box and power switch are never where they were last time, and a run can take place by day or by night, in clear weather or in a storm.
Players survive each round of zombies and spend the points they earn on doors, wall guns, perks and the mystery box. Guns are made stronger at the Gun Ascension altar, and after every round the player picks one upgrade from a draft, so each run builds differently. Zombies lose limbs where they are shot, and special enemies join the horde in later rounds: the Juggernaut, the Lope and the Skitter. A hidden Easter egg quest leads to a boss fight with the Mother. Beating her takes the party down to a second kind of map with everything they have, where a second boss waits.