John Grammaticus

John Grammaticus is a human operative of the Cabal, gene-mutated by them to become a "Perpetual" (immortal). He is also a natural psyker whose main psychic trait is as a powerful logokine, able to understand any language and the use, and power, of words.

Origins
Grammaticus was born on Terra, at the close of the 29th Millennium, in the Caucasus area. He had served as a line officer in the Caucasian Lewies, a Unification-era force that had allied with the Emperor during the Unification Wars. He met the Emperor, who recognized that Grammaticus was a man somewhat like him, and who said that they should have a discussion about the paths open to men with their particular "talents." This never transpired, however, as Grammaticus apparently died when he was hit by a car shortly after. He was reanimated by the Cabal, who offered him immortality in exchange of service, a deal to which Grammaticus agreed to.

The Cabal
Grammaticus was eventually shown the Acuity, and came to share the Cabal's "long view" of the Universe. Although fond of humanity, and wishing to help in fending off Chaos, he was appalled at the Emperor's "bloodthirsty" nature, which loosed the most terrifying killing machine (the Space Marines) on the Galaxy. Grammaticus was unusually compatible with the Cabal (possibly because of his psyker ability), and a succesful longtime operator, which was very rare among the Cabal's human agents. At over a thousand standard years old, and shortly before the Horus Heresy, he was asked, as one of the few remaining human agents, to convince the Primarch of the Alpha Legion to meet with the Cabal, who wanted to recruit the Legion in their war against Chaos -- a matter of some urgency due to the imminent corruption of Horus.

The Alpha Mission
After several setbacks and twists Grammaticus finally succeeded into arranging a meeting between the difficult and manipulative Primarch and the Cabal. Alpharius however had used a "honey trap", a beatiful Uxor (Command Staff) of the Geno Five-Two Chilliad, to manipulate Grammaticus in order to gain the upper hand in his dealings with the Cabal. The Uxor, Rukhsana Saiid, was a secret human operative of the Alpha Legion; Grammaticus fell in love with her, only to be taken advantage of by the Alphas. With his mission succesful, but emotionally a wreck after his love proved to be a lie, Grammaticus walked out of an airlock without a spacesuit, hoping to end his immortality once and for all.

Oll Persson
About two years later, and apparently still in the Cabal's service, Grammaticus was tasked with re-activating Oll Persson, another human Cabal agent and old friend who was also a Perpetual -- though Persson's immortality was the result of genetic, not Cabal-engineered mutation. Grammaticus psychically contacted Persson, who had retired at Calth, just before the infamous Calth Atrocity. Persson eventually heeded the call and left Calth, seemingly to meet with Grammaticus or/and the Cabal.