Grover Underwood is a satyr and lead Annabeth Chase, Jasmine Saturday, Luke Castellan, and Thalia to Camp Half-Blood in The Gift of a Best Friend. He made his first appearance in We Meet the Hunters of Artemis.
- We Meet the Hunters of Artemis
- Thalia Gets Turned Into a Tree
- I Get Claimed
- I Meet My New Brothers and Sisters (mentioned)
- My Never Ending Visions (mentioned)
- Cassandra is Leaving (mentioned)
- He is based on a character from Percy Jackson and the Olympians.