Shadows:
Heart: Oh the survivor's guilt here is intense and over a decade strong. There's also a lot of resentment and his trust issues just got exponentially worse.
Head: Nyx has some fairly significant PTSD. His flashbacks are mainly audible and he's very practiced in forcing back panic attacks by sheer life and death need. He's a soldier, one of the best, and has been on the front lines of a war with daemons for 12 years.
Other: This is probably going to be viewed as a shadow now? The extensive scarring on his left arm and fanning up onto his face is from wielding incredibly powerful light magic that was eating away at his body as he used it.
Light: He no longer has the power of the Lucii as a whole but he will still have a fraction of Regis' power in him. As the Kings draw their power from the crystal which is powerful light magic this may mean when he's channeling the power he might not be pleasant to look at for Shadow but it's not inherently his so probably not problematic most of the time. Until he tries showing off