The Return of Black Diamond

Steven has a dream of a fifth Diamond, one even more powerful than White.

Black Diamond.

He goes and tells the other Diamonds, turning out Black Diamond was real. She rebelled against Homeworld just like Pink did, except Pink wasn't a gem when Black had rebelled.

After Black was supposedly dead, White created Pink. But she rebelled too.

So they left it to three Diamonds and Steven.

But Black has returned and Steven's dreams seem to become reality.

He starts to worry about what happens next when he dreams about Black corrupting White.