Jasad was a Cardassian in the Cardassian Guard, Seventh Order during the late-24th century.
In 2369, he commanded a Galor-class cruiser, and led a group of three Cardassian warships to Deep Space 9 after Gul Dukat's starship had seemingly disappeared.
Believing that Deep Space 9 had somehow destroyed Dukat's ship, Jasad opened fire on the station. Upon Dukat's return through the Bajoran wormhole, he ordered Jasad to stand down. (DS9: "Emissary")
Gul Jasad was played by Joel Swetow in his first of three Star Trek appearances.
The script for "Emissary" describes Jasad as "arrogant" and, in one scene, "incredulous, but calm." 
In the Star Trek: Myriad Universes novel, A Gutted World, the mirror Jasad and his ship visited Terok Nor for repairs in 2373, though mirror Damar had to delay them, instead focusing efforts on getting the anti-proton scan sensors online.