John Grammaticus

John Grammaticus — a human operative of the alien Cabal, genetically remade into a Perpetual (a reincarnating immortal) and a natural logokine psyker, able to understand and weaponise any language. He was more than a thousand years old at the start of the Heresy; the Cabal charged him with putting Alpharius and Omegon in touch with it, hoping that through Horus’s victory Chaos itself would ultimately be destroyed.