- "Hah! I am better than good. I am the best. I am the Warrior."
- — Scathach in The Magician
Scathach is a Next Generation Vampire who helps Flamel and the twins after he came to her secret dojo overlooked by her one-bedroom apartment, with Josh and Sophie. She is also The Witch of Endor's granddaughter. Her other relatives we know about are her twin sister, Aoife of the Shadows, and her uncle, Prometheus. She has a brother. The only thing known about him is that he has red hair and was born before the fall of Danu Talis, and is thus an Elder. Her mother is described as having red eyes. In the Enchantress, her father turns out to be Ard-Greimne. In The Necromancer it is revealed that her parents inhabit a Shadowrealm modelled after Danu Talis. It is unknown if the Elder Hel is associated with her, as she too calls Prometheus uncle, but has no relationship so far to Scatty at all.
She puts her age as around two thousand years, but her sister reveals that she has been alive since the fall of Danu Talis, being one of the first Next Generation born after the fall. She has travelled through multiple Shadowrealms, and has been locked up in the Underworld Shadowrealm by her great aunt, Hekate, for centuries, but eventually found the way out. She was the one who put Tutankhamen and King Arthur on the throne. Her legends and deeds are often confused with Aoife's, since they are twins and look very similar. Scathach admits to being a vampire, but reveals that drinking blood is one of the lowest forms of vampirism. Instead, her clan of vampires absorb emotions, so they "can feel alive." She displays this by absorbing Sophie's extra senses of pain and fear after she was Awakened.
When they are attacked by the Nidhogg in Paris, Scathach is captured and dragged to the riverside by it. As soon as Josh frees her, she jumps back in to fight with the Valkyries, but is caught from behind by Dagon, Machiavelli's subordinate, and dragged into the river. Later, Sophie worries about her but is told she does not need to breathe, and that she is invincible.
Scathach has her roots in Celtic (specifically Irish) mythology: She is known in the myths for having trained Cúchulain (Cuchulain, Cu chulain or Cú chulain) on the island of Scotland. She also gave to him a spear that when thrust into an enemy's stomach explodes into many spikes, effectively killing him quickly and painfully. Cuchulain was also known to be her lover-- and her twin sister's too, Aoife of the Shadows, a well trained warrior as well. The siblings then had a falling-out, and had a fight while in battle along with Cuchulain who was killed in the battle and could have been saved if they had not fought with each other. They have not talked to each other since Cuchalain's death, which Josh and Sophie soon find out from Aoife in "The Necromancer."
Scatty has trained the greatest warriors of all time and is feared even within the ranks of the Dark Elders. She relishes the chance to display her combat abilities; specifically with two twin short swords that she is well proficient in. However, Scathach can use just about every weapon there is and is the inventor of all the modern-day martial arts; therefore, she fights with no style at all. She is stealthy, agile, frightening, and in some instances, "alien."
Scatty is one of the Next Generation Elders, but believes that the time of Elders is past and the world belongs to the humans now. She works with Flamel and regards him almost like the father she does not remember. She said that she was about 2,500 years old but Aoife, her twin, says that they were 10,000 years old and that Scathach is a terrible liar.
Scatty is described with the appearance of a 17 year old teenager, despite the fact that she is much older. She has short bright red hair, green eyes, incredibly pale skin, dabbed with freckles which masks her nose and contrasts her skin, rendering the freckles blood-red; along with a vague Irish or Scottish accent. She has a dark gray aura and also has a close relationship with Joan of Arc, gained when Scathach saved Joan from being burnt at the stake. Joan was made immortal when Scathach donated some of her own blood to the fellow warrior. Her eyes are noted to be unblinking.
- Immortality: Scathach is Immortal and does not age. Though an immortal may be poisoned or slain in battle, they may live for thousands or millions of years.
- Aura Manipulation: Scathach has learned to control her aura to a certain extent. She is able to shape the aura around her body, and uses it to power her magic.
Scathach holds many different weapons, but is usually depicted as having twin blades and nunchucks. She also is the master of martial arts, even claims to have created them, and has trained all the great warriors of the world, including Ninjas (which her twin, Aofie, despises, because she thinks they are very cowardly).
- Scathach and Aoife were mentioned being trained by Tsagaglalal in the Enchantress, saying that Tsagaglalal may be a better fighter than Aoife or Scathach.
- Scathach often boasted that no prison could hold her, but in The Warlock it is revealed that there is one that can keep her in: Danu Talis's active volcano prison.
- Scathach is a weapon master usually wielding a nunchuck and two twin swords
- Scathach has teamed up with Billy The Kid on at least one occasion, in "Billy the Kid and the Vampyres of Vegas".
- It is possible that Scathach was known in the Indian Subcontinent as Kali, given that she claims in The Magician that she earned the Title "Daemon Slayer" by killing a Demon called Raktabjia, which was killed by Kali in Hindu myth. Curiously, Kali is often depicted with blue-black skin, black hair, and four arms (none of which are traits that Scathach possesses) and is known to drink blood (which, despite being a Vampire, Scathach doesn't).