Clea

Clea was a witch and a member of the Grand Coven. She also an ally of Rowena.

History
Clea is very old and advanced witch that lived since Ancient Greek era and very well learned Ancient Greek school of magic. At some point, she befriended with Rowena and together, they have various journeys through the ages. The relationship still remained in "good terms" even after her expulsion from the Grand Coven eventually.

At some point, she made her way to Grand Isle, Lousiana and operated here. Rowena later tracked her to her lair in order to compose a spell that powerful enough to incapacitate The Darkness, so giving them some buying time before what Rowena-called "The End of Magic".

Season 11
After found her, Rowena asked some help to compose a spell. At first, she resisted to giving help, but realizing the end is nigh coming, she later agreed to help Rowena.

Realizing if they effort to buying time is useless due to how big The Darkness is, thanks to Sam efforts, she later agreed to teamed up with The Winchester team in order to stop The Darkness and claiming if she served the both God and magic side. She also enlisted some Grand Coven members to compose the spell.

After The Darkness lured by Rowena to the intended trap site, she and her team cast the spell and relayed it to Rowena so The Darkness can be weakened enough. However, they efforts just last temporarily. The Darkness relayed back the spell and make it backfired. Cooked Clea and her team alive, ending her long long life.

Powers and Abilities
Clea wass very old and advanced witch. Her extent of her power was unknown, but Rowena giving her very high respect due to her mastery of magics.
 * Immortality - Clea was very very ancient witch and has lived since ancient Greek era.
 * Magic - Having mastered many styles of magics and very well learned Ancient Greek school of magic, Clea able to cast many spells during her lifetime. She able to read future using Tarot Cards. She also able to compose a spell that able to deter even The Darkness to certain degree.
 * Super Sense - She able to aware of Rowena spying method.