In an effort to secure the space station Terok Nor against Bajoran Resistance insurgents, Dukat created a counter-insurgency program which activated a series of pre-programmed events intended to quash any uprising of the station's Bajoran workforce.
As part of this program, Kell secretly added a subroutine to rescind Dukat's command codes, as a precaution in the event Dukat ever tried to abandon Terok Nor himself.
Dukat did not find out about Kell's modification until 2371, when the program was activated on Deep Space 9. Kell's recording played and his final remark to Dukat was "try to die like a Cardassian". (DS9: "Civil Defense")
Legate Kell is briefly mentioned in the Pocket DS9 novels The Art of the Impossible (part of the Star Trek: The Lost Era series) and Fearful Symmetry, the latter of which describes him as being a stocky man with iron gray hair.
The Star Trek: Terok Nor novels Day of the Vipers and Dawn of the Eagles give his first name as "Danig" and recount his career prior to and during the Occupation of Bajor, from the 2320s until the 2360s. The novels reveal that Kell was the commanding officer of the starship Kornaire (an early posting of Dukat's) and the space station Terok Nor. The two officers had an adversarial relationship and frequently undermined and berated each other. The novels go on to describe a plan by Kell to quash the Bajoran insurgency during the Occupation which ultimately backfires on him.