Who is Scathach from The Magician and what is their importance?

Scathach is a warrior who once lived in Danu Talis. After seeing what the Elders and their companions were doing to the humans on Earth, she decided to go to Earth to protect the humans who could not protect themselves. This caused a great deal of trouble for Scathach among her family members and others she left behind on Danu Talis, and she has spent thousands of years fighting against those she once called family and friends.