Grayson is a student at A Nigma High. He is in a wheelchair and is part of the Genius Club. His office is located in a boy's bathroom stall where he keeps a stack of homework reports and essays that he sells to fellow classmates like Camillio Martinez Cyrus Xavier.
Grayson's official appearance was in Tales from Decrypt with the rest of the Genius Club. He took offense whenever he was called a nerd preferring to be called a genius. It was in The Curse of Earl Nigma where we first saw that he sold reports to the students, selling Cam a report on the three musketeers that he wrote. When Cam was blackmailed into stopping the protest in Fence-O-Palooza Grayson told him he didn't know anything or how someone could have gotten those pictures, and that if he (Cam) went down so did he, that being a cheater wouldn't look good in his record. Later on, he too received a letter telling him to make Cam stop the protest or he and all the others would go down for cheating. Grayson keeps a list of all the students that have bought him essays for "protection". In Bed Bugged the Blackmailer sends a note to Grayson telling him he might be spared if he doesn't reveal any other names on the list.
This however is all a ruse. Grayson himself is the blackmailer, he faked being a victim by "blackmailing" himself, took photos of his victims cheating from his office (which explains the angle), started to type his letters after Cam and Cyrus noticed the smiley face, pretended to try and hack his own account, and then when he scanned the fingerprints of the suspects, he secretly looked at Cam, Cyrus and Brandy with an evil smile. His reasons for doing this have something to do from back when was bullied in the 3rd grade by and with his victims. The answer was revealed in Revenge Of The Cycle Killers.
Apparently, Grayson was bullied during his elementary years, and by the same people who he was blackmailing (an exception may be Cam who showed in flashbacks to be unintended). In flashbacks by Cam it shows that Grayson even used the same bullying treatments that some of them used on him. While he managed to evade and escape Lee and Brandy the day Camillio was suspended, the day after he says he has been so filled with guilt of his own bullying that he had to come over and apologize. He promises to make it up to Cam