Three Powerful Witches

The Three Powerful Witches is one of the legends told by Selina.

History
Selina tells the Trix that she has a way to let them go into the Legendarium World and tell them the story about the Three Powerful Witches.

"They had an insatiable appetite for power, and they hated everything good, especially fairies."

Season 6
In "Mystery of Calavera", Selina and Acheron made up this legend so the Trix can enter the Legendarium with their role as "Three Powerful Witches".

Magical Abilities
It is unknown what is the ability of the Three Powerful Witches, but it is most likely that Selina or Acheron made up this legend so that the Trix can enter the Legendarium, with their role as "Three Powerful Witches". It was supposedly used to strengthen the Trix's powers and let them enter the Legendarium World.