Finding Searing Exarch

Im having a brain failure. How do I get the Searing Exarch influence on the map device?

I have the Eater of Worlds. The Envoy showed up at the entrance to the map and after killing the boss I received the item which added the influence to the map device. However, I dont have the Searing Exarch influence. The envoy hasnt shown up again.

Im currently doing T15s with 102 map completion and am ruining all maps with the Maven witnessing fights.

Run a few maps under Eater influence and Maven should show up, offering the item needed to unlock Exarch influence - as long as the maptier is high enough that is.