Regular

Then the dwarf’s gaze fell on Vimes’s arm, and he gave a groan and took a step back, raising his hand protectively.
“Yes! I’ll do it! Yes!”
“See that you do,” said Vimes, taken aback. Then he, too, looked down at the inside of his wrist.
What the hell is this?” he said, turning to Bashfullsson.
“Ah, it left its mark on you, Commander,” said the grag cheerfully. “An exit wound, perhaps?”
On the soft underskin of Vimes’s wrist, the sign of the Summoning Dark blazed as a livid scar.

– the mark |
Terry Pratchett, Thud!