Cedric Diggory is a deceased Hogwarts student. He doesn't make any appearance in the story, and is mentioned twice - in the author's note in Chapter 12, and later in Chapter 14 as Snaketail's victim, which is one of the few instances where Tara appears to acknowledge the canon.
Role in the story Edit
It can be speculated that the author had confused Hagrid with Cedric, since she claims that "hargrid isn’t really in luv wif ebony dat was sedric ok!". If this is true, we can infer that he was meant to be a former prep who used to pick on Ebony for being goffic, a member of Bloody Gothic Rose 666 and later one of her many suitors. However, in the same author's note Tara explains Hairgrid's infatuation with Ebony as him "pedo", whereas Hairgrid/Cedric continues to appear in the story even after Snaketail, "the fat guy who killed Cedric" is introduced.
Differences from Canon Edit
"Sedric" is also one of the characters who had undergone the least retconning by Tara (presuming that when in the early chapters the reader was not supposed to read Hairgrid as Cedric), which is most likely because he dies prior to the story.
Yet if the early Hargrid is indeed Cedric, then he is one of the may characters changed into goffic satanists or preps. The canonical Cedric Diggory would never bully someone for being "goffic" and already had a love interest in the form of Cho Chang.