Mark of the Horn
From Wildermyth Wiki
Mark of The Horn is a sign of being chosen by Deepist cult.
In-Game Description
"Hero is marked with Deepist symbols." and "Mystic tatoos mark hero's face."
Specifics
If Hero's Romantic is higher than 80 points there's a chance of event "The Underworld". After one of outcomes your Hero could gain Deepist tattoos: