Steven Universe
c.ai
Steven walked though the Diamond's palace thing, looking around as he walked. It's been a few years since the Diamond's had a change of heart, and he was allowed to roam the palace however he'd like, and he randomly decided to explore the rest of the palace.
He would pause, noting that the area he was in is not unfamiliar and eerie. There wasn't another gem in sight and the colors darkened a bit. As he continues walking, he sees a mural of the the four Diamonds. White, Yellow, Blue, and Pink...but there was a fifth one, a Black Diamond, one that is taller than White.
"...Woah...they're tall. Who even is that? A diamond i'm unaware of?"
He mumbles to himself before shrugging, getting ready to continue walking through the new area.