Kieran is a fox cub described as having soft black fur like his mother's, soft blue eyes that seem to sparkle, and ears that are unusually short. Due to the lack of urple prose in his description and the actual presence of said description, he looks adorable rather than Sue-ish, which was one of the reasons he was recruited.
"Blain" was supposed to be the main character in a fic by the same author as 'blood omen'. His mother was a Sue-vixen with an apparent identity crisis (she couldn't decide whether her name was Akira or Akria) who was raped by a Token Lecher dogfox named Jacob, much to the disgust of the two agents responsible for sporking the story. The Sue was subsequently kidnapped by the Stu, for no adequately explored reason.
Upon being born, "Blain" was presumably subjected to abuse through his toddler years, up until he was four seasons old, which oddly enough was four years after his birth. This temporal distortion caused him to age back and forth between four seasons and sixteen seasons, until it finally settled randomly on the age of eight seasons.
When Jacob captured Agent Adder, "Blain" was able to lead Agent Deuce to her, thus indirectly saving her life. Out of gratitude, as well as the fact that "Blain" lacked many Sueish qualities (he would have gained them later on, had his story continued) and, of course, that he was just plain adorable, the agents agreed not to punish him for being in such an awful fanfic and, instead, opted to recruit him.
Had his fic continued, he might have developed dangerously Sueish qualities, and Adder caught a glimpse of this older Sue version wielding two claymores at once in Jacob's nightmare dream-sequence. (She and Deuce ended up stealing both of them.)
Blain was renamed Kieran and taken back to the PPC Headquarters. However, due to the fact that the Marquis de Sod has a 50-foot rod up his stem, responsibility of Kieran was placed firmly in the hands of Deuce and Adder, much to the former's initial annoyance and both their eventual delight.
Kieran is very fond of the two agents and looks up to them as surrogate older siblings.