European and North American World of Warcraft players worked cooperatively to solve a puzzle that ultimately led to a Legion world boss spawn. Traveling throughout the Broken Isles, players discovered a series of orbs that, if clicked in the correct order, spawned the world boss named Kosumoth in the Eye of Ashara zone.
Kosumoth currently spawns every five minutes and can drop a toy or a mount IF players are attuned to be able to loot him.
EU and North American players worked together via a WoWhead chain of discussion to unlock Kosumoth for both regions. Devs have promised that there are a lot of secrets for Legion yet to be uncovered.
Check it out at the link above, unless, of course, you want to discover the attunement path to be able to loot anything from Kosumoth. In that case, ignore the link for spoilers.