Grimlock wears dark clothing, which gives off an aura of mysteriousness, and a hat. He also wears glasses, has short black hair with long bangs and is relatively tall.
Grimlock had apparently loved his wife, Griselda, greatly. However, unlike Grimlock who was constantly scared of death, Griselda did not fear death as she played Sword Art Online and was notably more lively living in the game than she was in real life. Grimlock apparently felt that Griselda had loved the game more than her husband and, in possibly desperation due to the fear of death, he killed Griselda as he believed she no longer resemble the wife he loved in real life.
Sometime in the past, before the events of SAO occurred, Grimlock married Griselda and they were happy together for a while.
He was the one responsible for the death of Griselda, his in-game and real-life wife. He killed her because he did not like the change in her personality. At first, he didn't want to aid Caynz and Yolko in their plans to catch Griselda's killer by forging them weapons to use in the in-AREA murders, but eventually he did, though not with good intentions. He helped so he could have Caynz, Yolko and Schmitt together and get them killed with the help of the infamous red guild, Laughing Coffin. However, the plan failed, because Kirito realized the truth of Griselda's death in time, and came to rescue Caynz, Yolko and Schmitt. Grimlock was then caught by Asuna.
It is unknown to what happened to him in the remaining time of SAO, but in the end, he was among the remaining 6,147 survivors of SAO.
In the 14th episode of the anime, his name appears briefly as one of the players who logged out.
Grimlock talking about his plan.
A scan of Grimlock's design from the Design Works artbook.