Greypatch was a one-eyed searat who was originally the first mate of Gabool the Wild, being Gabool's best steersrat. He wore a velvet patch over his missing eye and was a skilled swordfighter. After he determined Gabool was insane, Greypatch stole the Darkqueen with a crew of others who wanted to escape Gabool's madness, they ended up in Mossflower Woods. Several of Gabool's ships were sent after him, including the Rathelm and the Greenfang. It was here he discovered Redwall Abbey, and wanted to take it.
During this time, failed attacks on the Abbey lowered crew morale. Bigfang attempted to fight Greypatch for the position of Captain, but Greypatch killed him.
Greypatch failed to take Redwall, and was killed by the lance of Oak Tom in revenge for the deaths of Colonel Clary, Brigadier Thyme, and Pakatugg Treefleet.
Note: Greypatch's name is alternatively spelled Graypatch in the book.