How to get Searing Exarch on map device ?

I play on standard. I have 117 / 117.
I have 2 wheels on my map device - Maven, and The Eater of Worlds.
I miss - Searing Exarch.
What I have to do ?
Please help me ?

Follow the questline (open your quest window and read what to do)

I had the same problem, but with missing the Eater. I found the Exarch thing around yellow maps and just continued with the Maven stuff.

Did my first T16 today and was wondering when the Eater might show up. Apparently you have to do a couple of T9/10/11+ maps with the Exarch influence on the map device to make the Eater show up (or vice versa).