Funcom and Petroglyph have revealed their co-op multiplayer and challenge modes in the game. They co-op mode seems to be a very challenging concept where enemies come at you relentlessly where you and a friend play together to defeat those waves. The developers have limited it to two players only as they say it will just become overwhelming to manage too many players against even more hordes of armies coming at you, they describe two as being pretty chaotic as it is! Within the multiplayer mode, you will have to manage your resources between your co-op partner as well, and that really adds to the co-op element.
They have also announced a "challenge"mode whereby you can send a "challenge link" to a friend or other player where they can play the exact same map and exact feats that you have unlocked. So the test here is to beat your competitors and to paraphrase Mike Legg here about a potential scenario whereby streamers can send their challenge links to their follows and the game will create a leader board that everyone can see who can get the highest score.
You can watch the video here for yourself, the release date for the game is 30th May so not long now until the great hordes are unleashed upon us!