Phorcys

Pegasus and Chrysaor have a twin sister only Jupiter knows about named Phorcys after Medusa's mother. She looks exactly like Pegasus but black and has been following him and Emily on their adventures, but when the nirads attacked New York she got captured by the CRU. eventually she shared a cell with Stella, Earl, Frankie, and Agent B. Will she escape, reveal she exists, help the Olympians fight the mutant titans and cause chaos, or will she stay in the shadows forever?

I don't own all of the characters, Emily, Pegasus, Jupiter, Stella, Earl, the CRU, Frankie,