Fiona

"I hear fairies make wonderful mothers."

- Evil Queen

The Black Fairy, also known as the Dark Fairy, is an episodic character on Once Upon a Time. She was once one of the most powerful fairies that ever existed, residing back in the Enchanted Forest. She is known to have once possessed a very powerful wand, but had it confiscated after being defeated by her nemesis, the Blue Fairy.

Before the Curse
"One of the most of powerful fairies that ever existed. Well versed in the dark magic. The Blue Fairy exiled her, but before she did she took her wand."

- Tinker Bell

At a time, the Black Fairy was very powerful - one of the most powerful of fairies to have ever existed - and extremely well versed in dark magic. When on the run from the Evil Queen, Snow White goes to the Black Fairy for help, which is provided in the form of fairy dust. This dust is said to have the ability to turn the most fearsome of adversaries into a form that's easily squashed, something that would eventually come in handy for the runaway princess. At an unknown point after this, the Black Fairy battles her nemesis, the Blue Fairy, and ultimately loses. As punishment for her crimes in the past, the evil fairy is exiled and her wand is confiscated. ("Snow Falls"/"Going Home")