Samuel Liddell Mathers (サミュエル・リドル・メイザース Samyueru Ridoru Meizāsu) is a teacher at Stratford school, and a former member of Hand of God. He offers to teach William Twining and Isaac Morton magic. It's later revealed that he's one of the Four Horsemen of the Apocalypse, most possibly the Red Rider, who represents War.
Mathers has curly hair, split in the middle, that reaches just past his shoulders and is tied back in a low ponytail. He has a hight forehead and somewhat narrow eyes, framed with thick, dark lashes. Mathers is fairly tall and slender.
He's very knowledgable, seems rather playfull, and a lot about him and his motivations is still shrouded in mystery. He wants to strengthen the human race, which was always intimidated by Heaven and Hell. He is very knowledgeable, and knows a lot more about Heaven and Hell than an ordinary human should.
He appears to have grown fond of William (and Isaac), and is invested in getting him stronger.
After leaving the Hand of God, he proclaimed himself the Count of Glenstrae. Not long after, he appeared before William, offering to teach him magic. He left when William told him he'd think about his offer, but not before seemingly effortlessly breaking a barrier that surrounded the estate.
We see him next in William's school, as a teacher (for Latin), where he starts teaching William and Isaac magic.
Real name: Samuel Liddell Mathers.
Founder of Hermetic Order of the Golden Dawn, a secret society for modern Western ceremonial magic. Calls himself for Count of Glenstrae. By joining the Freemason, he researched occultism on full-scale.
He also joined Societas Rosicruciana in Anglia, where he met Westcott and Woodman. These three established the Hermetic Order of the Golden Dawn. Later on he translated and edited the grimoire "Key of Solomon” to english. He excelled at art of war along with occultism. His hobbies is chess, boxing and fencing.Isaac: Woooow♥
How can you enter the Hermetic Order of the Golden Dawn!?
Mathers: Hm. See the advertisement for the bulletin Lucifer, and give a contact maybe. I mostly invite the guests in British Museum.
Isaac: Eh? No decoding some secret note, to reach it?
Isaac: The headquarters being at the end of a underground labyrinth?
Mathers: No. But that’s club activities…
Note: Early days of Golden Dawn was more like club for those interested in occult.“ 
- "The categorisation of Angels as Good and Demons as Evil has no basis. They are neither Good nor Evil. They simply use their own abilities in a fight for territory in this land."
- "It [magic] is neither fairness, impartiality nor justice."
- "Wisely, and slow; they stumble that run fast."
- "I want to strengthen the Human Race, which has been intimidated by Heaven and Hell since Time began."
Amon and Mamon • Baphomet • Eligos • Gilles de Rais • Gilgamesh • John Dee • Lamia • Leonard
Belphegor • Empusa • Lamashtu • Leviathan • Lucifel Rofocale • Pluto • Astaroth the Second • Behemoth
Adrian Swallow • Barton Twining • Bianca Clifford • Elliot Eden • Mary • William Wynn Westcott
Arthur Christian • Cassandra • Ernest Crosby • Tamar • Elizabeth Dale