Delta the 5th Horseman
Riding with The Four Horsemen is a (sometimes) woman.
She can't seem to hold a form for very long, leading many to believe she's a Mirrorskin.
She answers to a different name each time.
"I didn't do it!" or Quotes
"I'm bored." - Delta... "Shit." - everyone else.
Garth Brooks - "She's Every Woman"