Midnight is a character I had been working on for a while now. She is a kind of a hybrid between an evil Changeling, a reformed Changeling and the Tantabus.
During the episode "Do Princesses dream of magic sheep?" Rainbow Dash had a dream where she fought a number of Changelings. It was stated that the Tantabus could infect the dreams of others if they dreamt about them, but these unnamed Changelings were never addressed.
What if after being defeated, what if part of the Tantabus had fled into one of those Changelings to hide? Laying dormant until Midnight was reformed. During the transformation, she was halted halfway through and the essence of the Tantabus was fused with her. Creating a creature that was a fusion of all 3 entities.
Midnight has some control of the Tantabus' power. She can use it to transform others and inanimate objects as well as herself with her natural Changeling shapeshifting. Creating illusions to go along with her dancing and music.
She is learning to use her newfound dream abilities and use the Tantabus' nightmare magic for good.
While working on her, I kept coming back to the song "Gypsy Bard" so I couldn't resist giving her a tambourine and a gypsy inspired outfit.