Being a squad style shooter, Catacombs was built with online play in mind. You can complete the game solo and there is a story to follow, but Cavia also created a bunch of multiplayer modes. The main online mode is co-op where a group of four players progress through the levels. If a player goes idle or drops out s/he is replaced by the computer. In the middle of a level run, players can vote to change the difficulty level (easy, normal or hard), restart a stage (to collect item drops) and kick other players. Catacombs also has a standard deathmatch mode and assault mode where you have to defend a room until time runs out.
Another multiplayer mode called Exterminator locks four players in a room with traps and friendly fire is turned on. You can shoot each other, but that isn’t the goal. You have to take out enemies spawning from generators around the room. Players earn points for each downed monster and a huge bonus for taking out Titan or Reaper class enemies. You respawn if you get shot down and the game ends when time runs out.
The most interesting mode is called Maze, which a Cavia developer says its inspired by Pac-Man. Four players are thrown into a maze with corridors so narrow its difficult to turn around. Ghoul enemies (melee monsters) appear and chase you. While you have your gun, you don’t have any ammunition. Touch a small dot and you can fire for three seconds. Eat a large dot and your weapon upgrades to its max level for five seconds. The goal of Maze mode is to eat eight pieces of fruit scattered in the maze. Fruit appears randomly, but unlike Catacombs’ usual levels there are ten or so different maze patterns. Other enemies like a Huitzilopochtli aren’t restricted by the walls and fly through the maze.
Going back to the core game, Catacombs has a couple of different environments to shoot through like Ancient Greece, an Aztec temple, and a stage based on Angkor Wat. Before you begin each level you have a chance to store a weapon in a safe box. Place it here and the weapon will be waiting for you even if you die or restart the game. Sort of like Demon’s Souls, Catacombs takes away all of your magical gear if you die, leaving you with a plain pistol.
Each area has unique trials players will face, but they won’t see everything since levels are randomly generated. In Greece you have to sneak through a pitch black room while sentries scan the area with searchlights. If a light spots you, you’re warped outside. One player can switch off the spotlights, but this usually require other players acting as a decoy.
In the Angkor Wat area players have to walk through rooms filled with tall blades of grass that block your field of vision. You have to defeat all of the monsters to leave and if you’re quiet you can take them out with magic or decoys. Noise aggravates monsters prompting them to attack players. The Aztec area has fire spitting statues that ignite oil slicks creating fire walls players have to navigate through. One option, the source says, is to have a really strong healer cast cure while everyone advances through the flames, but that player would need to have practiced using the spell for quite some time.