life ain't always fair

His eyes turn red when he uses his demonic cultivation. Almost always going to be carrying around a bamboo flute and a sword.

He gives off some dark/demonic pings when he’s using his abilities, since it's all resentful energy. Feel free to also sense that this body definitely does not belong to his soul. It does now but it didn't before.

He has the ability to use resentful (or "demonic") energy to control undead beings and spirits! My default is to not have this impact player characters in any way--the nature of the spiritual energy in a different world is different enough to handwave otherworld-y interference, etc. But if you do want to have that be something that your character is pinged by at all, feel free!