Zephro Carnelian is a human Illuminatus, and a liaison between that organisation and the Eldar. As an Illuminatus, he is as comfortable in the Immaterium as he is in realspace. He seems to be enamored of Eldar culture and knowledge, especially as it relates to Harlequins. Indeed, he is shown to favor Harlequin dress and mimick their mannerisms. He also acts on behalf of the Illuminati and their Eldar allies as a double agent, having infiltrated the Ordo Hydra.
He was the prime operative in a plan to manipulate secret Inquisitor Jaq Draco into an unwilling triple agent - as an Inquisitor who's furthering the Illuminati's plans by joining the Ordo Hydra. According to the Eldar Farseer allies of the Illuminati, Draco was to be a significant actor in their common plans. Draco was also considered by Carnelian to be a prime candidate for "Illumination" -- joining the cabal of the Illuminati. In a feat thought impossible, Carnelian originally contacted Draco by remotely intruding into one of Draco's readings of the Emperor's Tarot and taking over the deck's Harlequin card. It is not known whether this was an ability acquired by members of the Illuminati or whether it was a particular psychic gift of Carnelian's alone. Carnelian's plans regarding Draco eventually backfired, to the dismay of his Eldar mentors and patrons amongst the Illuminati. Carnelian's current whereabouts and disposition are unknown.
- The Inquisition War (Omnibus Novel) by Ian Watson