Time After Time | Episode 10: Comin' Atcha Like A Fire Blade (Patreon)

No seriously what does "I'm comin at you like a Dark Horse" even mean? Like for real I'm not joking just tell me what you think it means. Like is the dark horse supposed to be scary? Or like that she's an underdog or something? Genuinely I'm lost I have no idea what that's supposed to mean.