Sondar was a male Klingon soldier who served in the Imperial Klingon Defense Force during the 23rd century.
Sondar looked like a hybrid of QuchHa' and HemQuch Klingons, and could belong to an unnamed splinter species.
In 2266, Sondar was among the personnel of a Klingon strike raider that brazenly attacked the much larger starship USS Enterprise in order to lure it to the planet Seggor.
Later, he carried the powdered remains of Enterprise crewman Hoskins to an underground laboratory. He then placed the powder near the granulator weapon, which reverted Hoskins to normal in front of Captain James T. Kirk. After being shown the power of this weapon of mass destruction, Kirk was ordered to surrender Earth to the Klingon Empire. (TOS comic: "The Klingon Ultimatum")