 Tyson is close with several characters and magical creatures in the series, including Rainbow the hippocampus, the hellhound Mrs O'Leary and the harpy Ella, who eventually becomes his girlfriend.In The Battle of the Labyrinth, Tyson is revealed to be afraid of satyrs, including Grover, he manages to conquer this fear after a quest and they become friends.Nico Di Angelo is first seen in The Titan's Curse, as an unclaimed demigod rescued by Percy, Annabeth, Thalia, and Grover.