Unlike Campaign, Horde Mode is rather self-contained, despite having to be played online. The player is spawned in an area covered in control centers, and has to spend a certain amount of waves defending control centers, and surviving.
The player can achieve this by playing aggressively, or hanging back and working on crowd control.
As the player defeats enemies, acquires Wave MVP (multiplayer only), Turret MVP (multiplayer only) or flawless waves (no damage to the control centers), they earn Lien, which can be spent on buying turrets.
Turrets help the player defend certain locations, increasing their chances of completing the level. Players can purchase either machine gun, icethrower, grenade launcher or shotgun turrets, which provide various advantages and disadvantages to the battlefield.
Horde Mode is the only place where Mini Deathstalkers spawn.
Like Campaign, the more players are present, the more enemies spawn, therefore increasing the difficulty in certain senses.
At the moment, there are only 3 maps to play on for Horde Mode.
- Emerald Forest, 5 nodes over 10 waves
- Forever Fall, 3 nodes over 8 waves
- Mountain Glenn, 4 nodes over 10 waves
- There is an unused Horde Mode map for Dr. Merlot's Island
- The Horde Mode achievements are the most challenging to get, even though there are only 5 achievements directly related to Horde Mode
- Turrets do count towards Rank requirements, except Turret MVP does not count as Wave MVP.