Hey Nobal,
actually there are almost no references to what he looks like. I know that he himself only shows in one Event where he speaks to the player:
“The tent melts away, slipping into the folds of an immense and immutable darkness. The cultist is gone. In his place is a black cloak, its arms to your shoulders, a slate of granite for a head, its edges chipped and cracking. It appears there is something behind this mask, behind this futile effort to keep your mind safe from its true visage. A voice speaks, a guttural, booming voice that is yet narrowed into a brutish whisper only for you to hear.”
There are lost of quotes and discussions on the topic in the forum:(contains Spoilers)
https://steamcommunity.com/app/365360/discussions/0/3247565033759127870/
Cheers!
