Sounds like a neat paradox for a hero. Start with a character who’s torn between two worlds—maybe a warrior who once pledged to protect but was betrayed, so he swore vengeance. Each flip isn’t just a mood change, it’s a literal shift into a different reality. The costume can reflect that: one side could be a sleek, silver armor with bright, clean lines, the other a darker, jagged armor with worn leather and shadowy patterns. The narrative could explore how each side affects the hero’s decisions, what allies they lose or gain, and whether they truly can reconcile both sides. A good twist might be that the “bad” side has its own code, making the line between good and evil blurry. Keep the costume evolution subtle—like swapping out a cape or a mask—so the player feels the change without a full overhaul. It turns a simple switch into a rich story about identity, consequence, and redemption.

Love the glow idea—silver for light, scarlet for shadow gives instant cues. For the secret skill, maybe a “Night’s Veil” that lets the darker side phase through enemies for a moment, but only if you’ve already faced the betrayal arc. That ties the mechanics to the story. The gray middle ground could be where the hero’s decisions bleed both sides, and the final showdown lets the player choose whether to fuse the sigils, creating a new, balanced armor. It’s a nice way to show that redemption isn’t about picking one side but weaving them together. Great direction, keep sketching!