Me and some of my friends were talking a couple of nights ago about some ideas for this game... one major idea was focused around crucible. Imagine you're in the middle of a match of crucible and all of the sudden enemy come pouring in from all sides, and fighting(between players) temporarily subsides and now you must work together to defeat the enemy whether it is the fallen, hive, vex, or the cabal. If this were to become a thing it shouldn't happen to often because it would quickly get boring and bland, and some people obviously wouldn't like it.