Described by Kobliad Security officer Ty Kajada as "quite brilliant in his own way," Vantika was obsessed with prolonging his life and ensuring his own survival. The life-prolonging substances he used included rejuvenation drugs, cryogenics, and organ transplant. As the medical supervisor of a high-security penitentiary, he secretly used inmates for his illegal experiments in cellular longevity. As a criminal mastermind, he organized raids on government labs to steal bio-regeneration research. He evaded Kobliad authorities for twenty years, faking his death several times (often in ways that fooled even medical specialists).
Like all Kobliads, he needed deuridium to stay alive, and was planning to hijack a shipment of ore arriving at Deep Space 9 from the Gamma Quadrant, when he was captured by Kajada in 2369. In an attempt to escape, he started a fire in Kajada's transport that killed the pilot and severely weakened her. His own body was also fatally wounded, but he had perfected a means of transferring his consciousness into another humanoid brain (comparable to the Vulcan method of passing on their katras). Shortly before his body expired, he used the method on Doctor Julian Bashir, who had responded to Kajada's distress call, managing to hide his mind in Bashir's body and only taking intermittent control to limit the possibility that his deception would be exposed.
Occupying Bashir's body, he attempted to carry out his original scheme. He made contact with Quark (without showing his face), who had arranged for soldiers of fortune to take control of the deuridum cargo ship Norkova. The transfer was discovered after a series of crimes aboard Deep Space 9, including an attack on Kajada. When Quark and his mercenaries went to the USS Rio Grande to use it to hijack the Norkova, they found Bashir there, and Quark was stunned when he realized Vantika had inhabited Bashir's body. Vantika and the mercenaries beamed over to the Norkova, killing the bridge crew, but DS9 caught them in a tractor beam, surprising Vantika, who had attempted to shut down the station's computer and been thwarted by some unorthodox thinking by visiting Starfleet Lieutenant George Primmin. Contacted by the station, Vantika threatened to take the ship to warp while still in the tractor beam, which would destroy the ship and spread deuridum all over the Bajoran system. To prove his sincerity, Vantika killed his right-hand man, Durg, when he refused to go along with it. Fortunately, Vantika was incapacitated when Jadzia Dax managed to transfer an electro-magnetic pulse along the tractor beam specifically arranged to disrupt Vantika's neural energy patterns based on available readings, allowing Bashir to take control long enough to deactivate the shields and beam Bashir to safety. With Bashir's body stunned to ensure that Vantika couldn't do anything, Dax was able to transfer his consciousness from Bashir to a micro-containment field by configuring a transporter to beam out the glial cells contaminated by Vantika's patterns without harming Bashir himself.