Suvak was an ambassador to a planet in the sector which contained Hephaestus. He met Joanna McCoy during his eighth pon farr, mind-melded with her, and agreed to marry her. He had come to Hephaestus for a “rest cure,” and had officially hired Joanna as a private nurse, thinking he was suffering from some kind of virus. It turned out to be choriocytosis.
An underground facility manufactured intelligence-augmenting symbionts for the native Hephaestans. Klingon Commander Kagg knew this secret, and had planted a bomb in the facility. Kagg took Joanna McCoy as a hostage. Suvak used his mind meld to lead him to Joanna. He freed her and physically restrained Kagg while Joanna and a rescue party beamed away, moments before the bomb exploded, killing Suvak and Kagg. (TOS comic: "All the Infinite Ways")