Samuel Liddell Mathers teaches at Stratford school and used to run with Hand of God before moving on. He's the guy who offers to bring William Twining and Isaac Morton into the fold, teaching them magic. Turns out there's way more to him than that—he's actually one of the Four Horsemen of the Apocalypse, and the evidence pretty heavily points to him being the Red Rider, the one tied to War.
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