Grunk is a Cyclops under the employment of Caligula in Triumvirate Holdings.
The Trials of Apollo
The Burning Maze
When Apollo, Meg McCaffrey, Piper McLean and Jason Grace were captives aboard the Julia Drusilla XXVI, Grunk and a mortal mercenary named Florence stood flanking guard over the entrance to the yacht's interior. When Florence wanted to call in the presence of prisoners but Amax denied this until his interrogation was finished, Grunk finalized the argument that it would be Amax who would face punishment if the prisoner's escaped. When Apollo and his friends had killed their captors, Florence and Grunk came charging into the room, but Apollo swiftly shot Grunk through the eye with an arrow he later discovered to be the Arrow of Dodona, killing him.