Although we cannot tell you which iconic fairytale villain Mader will portray, (we're being kept on super-secret lockdown!) we can tell you that you will find out the twisted answer soon enough! Fans will get their first glimpse at the actress' evil ways when they tune-in to Once Upon a Time's mid-season finale airing Dec. 15.

Following the sure-to-be mesmerizing episode, Mader's fairytale identity will be revealed in an action-packed promo that will tease the long road of adventures our characters will face in the second half of the season. Trust us, you definitely don't want to miss this jaw-dropping reveal!

Once Upon a Time airs Sundays at 8 p.m. on ABC!