Kattell was a Cardassian woman fabricated by the Cardassian spy Seska.
In 2371, USS Voyager's EMH discovered that Seska's blood chemistry was not consistent with that of a Bajoran. She claimed to have survived a childhood bout of Orkett's disease due to a bone marrow transplant from a sympathetic Cardassian woman, named Kattell, who she claimed they could ask themselves if they ever returned home.
Her claims were ultimately proven untrue by expert testimony from The Doctor.(VOY: "State of Flux")
This character is only mentioned in dialogue.
Due to Seska's attempts to cover her identity, it is unknown if there is actually a Cardassian woman named Kattell. It's also conceivable that Kattell is Seska's own Cardassian name.