Maxwell’s tattoos are bound to his soul

[Maxwell] reached back and pulled the scrubs over his head. His shoulders and chest were covered with elaborate designs. Four smaller ones on his back framed a perfect circle of bare skin.
“I didn’t know Jarvis had so many tattoos,” said St. George.
“He doesn’t,” Max said as he shook out a pinstriped shirt. “I do.”
…
“The soul is all about identity, and the body is part of someone’s identity. Granted, we all tend to picture ourselves a little taller, a little thinner, but past that there are always physical things we just accept as an inherent part of who we are, and these are the things that are hard-wired into our soul. They carry over in cases like this.”
Max gestured down at his chest. “All these tattoos are part of me. It’s how I see myself. You could say they were inked into my soul as well as my skin. But if, say, Billie here came back, she’d probably only bring her Marine Corps tattoo with her, not the rose or the dolphin.”
…
“You’ve got a big bare patch on your back,” said Freedom.
“Because that one wasn’t supposed to carry over,” said Max. “Big, soul-scarring magic. One use only. If I can’t see it, it can’t become part of my identity.”

Excerpt From Ex-Communication, pg 261-262
Peter Clines
https://books.apple.com/us/book/ex-communication/id635706546