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 chief medical officer of a high-security prison, he secretly used inmates for his illegal experiments in cellular longevity. As a criminal mastermind, he organized the theft of top secret bio-regeneration research. He evaded Kobliad authorities for over 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 ship 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 (Compared 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. The transfer was discovered after a series of crimes aboard Deep Space 9, including an attack on Kajada. Fortunately, Vantika was incapacitated when Jadzia Dax managed to transfer an electro-magnetic pulse along the tractor beam specifically arranged to disrupt Vantika's synaptic 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 small containment field by configuring a transporter to beam out the brain cells contaminated by Vantika's patterns without harming Bashir himself.