[Reala is a particularly hard guy to mindfuck, given his nature, but you're absolutely welcome to try!
As a living personification of a Nightmare and someone who steals his canon's equivalent of souls, though, he's very well disposed to mindfucking others, no holds barred on level of nastiness, no personal motivation needed. Given that it's also in a dream, it's entirely feasible to assume the dream itself feeds him all the information he needs to know about your character and their fears/traumas/vulnerabilities--and potentially allows him to craft it into a perfect personal hell for them, if you'd like.
TL;DR: Reala is a good way to play around with potential grimdark scenarios you've been wanting but never able to get. Poke me if you want to plot~ ♥]
Reala - NiGHTS: Journey of Dreams - OTA
As a living personification of a Nightmare and someone who steals his canon's equivalent of souls, though, he's very well disposed to mindfucking others, no holds barred on level of nastiness, no personal motivation needed. Given that it's also in a dream, it's entirely feasible to assume the dream itself feeds him all the information he needs to know about your character and their fears/traumas/vulnerabilities--and potentially allows him to craft it into a perfect personal hell for them, if you'd like.
TL;DR: Reala is a good way to play around with potential grimdark scenarios you've been wanting but never able to get. Poke me if you want to plot~ ♥]