The only thing that I can say immediately after watching the trailer is that the theory that Azem created the key is looking very strong right now. It looks like we, the WoL, built a very unique looking portal by using the key + the Azem crystal.

This would fit because Azem probably knew of Venat's plans and created the key as a way to allow future Azem shards to continue adventuring across shards. However, they will have to explain how the other Ascians never used the key for their ends. Still a lot to learn but yeah, I'm subscribing to the Azem theory for now.