Seevus is the primary antagonist in the novel, Lightning the Argent. He is the owner of the Blackard Company that sells the Vitae.
Seevus first appeared promoting his medicine to Ky Kiske. He crushed a dog's paw and healed it instantly using the Vitae. Suspicious about the medicine and the disappearance of people, Ky headed off for an investigation.
Eventually, Seevus' medicine were actually Gear cells that invade the host's body. He was also responsible for Solaria's Gear conversion, and was planning to use her as a Command Type. Ky confronted him and he took his own medicine to transform into a large Gear. The two battled with Ky emerging as a victor and Seevus dead.