Gerhardt’s Ghost was a mysterious criminal who robbed, crippled, and assassinated various antagonists of the House of Gerhardt during the years Serin was away from Sterling. He gained particular notoriety for the enigmatic notes he left at the scenes of his handiwork to intimidate or taunt his victims (or their next of kin).
Currently, it is known to Serin that Gerhardt’s Ghost assassinated his grandmother on his father’s side, Margaret Lym Foley (of the Pillar House Foley) and her son, which could possibly be Serin’s father, Habbel Zon Holden.
Gerhardt’s Ghost had left a message with the the Foley family stating, "Two roads were open to you, one is now closed. You will die by the hand of Gerhardt’s Ghost. (signed “GG”)" This message was discovered on the orders of a group of Lord Honne’s soldiers by Serin Zon Gerhardt, who had stolen them.
Serin presumes that Gerhardt’s Ghost is the thief (or in league with the thieves) who stole Gerhardt’s Sword.
Serin discovered the identity of Gerhardt’s Ghost, which is in fact an organization.