In multiplayer mode, a team of up to four players must protect the core together. The health of the enemies scales with the number of player slots chosen by the host of the server but not with the actual players in the game, so teams with open slots are at a disadvantage.
The selection of enemies that appear in each wave is generated randomly, with some types of enemies having a greater chance of being selected than others. The first four waves only contain one group of enemies per wave, and the wave 5 contains two groups. In the rest of the waves, if the wave number is not a multiple of 5, then there are two groups of enemies. If the wave number is a multiple of 5, it is called a "heavy wave" and contains three groups of enemies, but less enemies per group. Multiple groups can have the same type of enemy.
In multiplayer mode, the following maps are available:
* DLC map. Players who do not own a DLC map can still join servers on that map, but they cannot host on it.
The difference between the difficulty levels is the amount of health the enemies have. There are three difficulty levels available when hosting the game.
|Creatures||Walker · Big Walker · Runner · Charger · Tank · Hoverer · Bobble Head · Soaker · Blocker · Spore Pod · Glider · Dodger · Spitter|
|Towers||Block · Televator · Lightning · Gatling · Scatter Laser · Anti-Air · Mortar · Slow Field · Amp Field · Holo · Killing Floor · Violator · Penetrator · Kairos · Accelerator · Drone|
|Weapons||Assault Gun · Freeze Gun · Sniper · Shotgun · REX · Tesla|
|Maps||Mine · Bridge · Arc · Glade · Complex · Facility · Aftermath · Aftershock · Cavern · Slums · Christmas · Yogscave · Corporation · Invasion · Chasm|
|Game modes||Single player · Multiplayer · Survival|
|Strategy||Level Maze Designs · Weak Spot|
|Insane difficulty guides||Mine · Arc|
|Storyline||Web Comic · Elysion One · The Old City · Brightsiders|
|Characters||Skye Autumn · Sweet Autumn · Jacksson Whalebrook|
|Miscellaneous||Achievements · Options · Coffee Stain Studios · Game Updates · Soundtrack|