Four emissaries are sent to a diplomatic meeting between 4 of the 5 clans: Tarjik, a Temur Loxodon Shaman. Gurcu, an Abzan Aven Shaman. Meshag, a Mardu Orc Shaman. And Kan Lin, a Jeskai Human Monk. The Sultai don't bother sending anyone.
The meeting is on neutral ground, ie Ugin's Nexus, and almost immediately they notice odd things going on and trek into the canyon to investigate.