Kai Zulane was an Astropath of House Castana serving aboard the Ultramarines vessel Argo at the beginning of the Horus Heresy. Unusual for an Astropath, Kai's eyes (normally lost when a psychic became an Astropath) had been replaced with augmetic implants, allowing him to see almost as well as his natural eyes.
When an unusually violent series of Warp Storms breached the Argo's Gellar Fields the ship was severely damaged and would have been lost had it not escaped the Warp at the last moment. Only Kai Zulane and Roxanne Castana survived.
Kai initially believed himself to be to blame for the loss of the Argo, as he had been transmitting a message at the moment the ship's Gellar Fields failed. He thought that his psychic connection had been the means by which the entities of the warp had breached the ship's defenses.[1g] The mental trauma, along with his guilt, prevented Kai from being able to send and receive psychic messages any further. Agents of House Castana were unable to rehabilitate him and so he was returned to the City of Sight on Terra.[1a]
While back on Terra, Kai was given intensive re-training to attempt to return him to his previous level of astropathic ability. His recovery was interrupted by the arrival on Terra of Magnus when he forced his way into the Emperor's Webway experiment in an effort to warn his father about the betrayal by Horus. The psychic explosion severely damaged the City of Sight and killed many astropaths.[1b] Kai's mentor received some sort of visions of the future in this moment, and imparted the secrets shown there into Kai's mind, hidden within Kai's own feelings of guilt in order to protect them.[1c]
Kai was taken to the Hollow Mountain to have these secrets forcibly extracted from his mind (a process which would kill him).[1d] He was able to resist this forced invasion of his mind but would eventually have succumbed had he not been freed by a prison break by several Astartes who had been on Terra as representatives of some of the Legions now known to have turned on the Emperor. These Astartes, led by Atharva, a marine of the Thousand Sons legion, took Kai with them as they fled.[1e] Atharva knew Kai had a valuable secret inside him and wished to gain control of it.
Kai was an unwilling companion to the fleeing Astartes (now calling themselves the Outcast Dead) as they fled through the Petitioner's City near the Emperor's Palace. Along the way, one of the Astartes, Ashuba of the World Eaters, realized Kai's augmetic eyes were being used to track them, tore them out of Kai's head by force, nearly killing him.[1f] Kai was able to survive after receiving medical attention.
Kai was eventually able to deliver the secret information to the Emperor psychically, after a series of visions in which the Emperor spoke to him directly. Once Kai was able to accept that he was not to blame for the loss of the Argo, and possibly due to his encounter with the Emperor, his natural eyes (a deep shade of violet) regenerated spontaneously.[1g]
Kai died in the Temple of Woe when he willingly sacrificed himself to prevent anyone from learning the secret that had been hidden in his mind. He asked Roxanne Castana to uncover her Third Eye so that he could look upon it, an act that was fatal to him.[1h]
- 1: The Outcast Dead (Novel) by Graham McNeill