Indelible
Percy had a fondness for tracing Nico's scars whenever he could, as often as he could. The indelible marks while not attractive, were proof that his lover was strong, a true warrior. He had survived so much. Sometimes Percy took his own invincibility for granted. In comparison, his Nico was delicate, fragile. At any moment, in any battle, Percy could have easily lost his precious Nico. Not that Nico agreed, he scowled when the older boy had mentioned it. "I'm the Ghost King! Not some damsel in distress." he mumbled. Percy only snickered. These scars made him Nico, which is the reason he loves the marks so much.