Ok, think about it. You, 5 other buddies, and 450 thrall, MAGICAL, but that's not all, after each wave (maybe up to 10) it gets progressively harder, each wave of thralls more so than before. Each wave the enemies are more difficult and more abundant, but after 5 waves, TAKEN thrall appear, and the final boss, A BIG THRALL! So I know your thinking, "what about loot", and not to worry my friends, because each thrall has a 1/10th of the chance to drop tokens that can be redeemed for the best of gear, like a thrall loin cloth for the big prideful Titans, a magical thrall friendship bracelet for warlocks, and a beautiful thrall carpet, just for the hunters! All of which will be redeemed at cayde, who will make jokes like "you killed them thrall gaurdian" or "get back out there gaurdian, thats not thrall!" And many more classics to come. Now I know you're thinking "oh dub, why not just make it so a combination of all the enemy types come after you, why don't you have rewards drop after every wave and at the end waves the the best loot chance, why not have enemies in vehicles come after us too?" Well, that's because thrall can't ride pikes. [spoiler](In all honesty I would like a serious horde mode type event for destiny 2, and using the Castellum would just be the best, especially since it's already kind of like a weird arena)[/spoiler]