Horatio Clayton was the brother of Byron Clayton and the husband of Moira Clayton.

He died before the Unhallowed Metropolis campaign began, when someone planted a bomb on his carriage.

Billy made a JRPG video game called Horatio's Story, which told some of the background story to the main tabletop roleplaying campaign, and where Horatio (still alive, at that point in time) was the main character.

He also appeared in the video The Birth of the Fandicade, when the game was released.