Bythos

Bythos is the combat trainer at Camp Fish-Blood a camp that has trained countless Mer-Heroes.

History
Bythos has trained countless Mer-heroes, including Triton, Glaucus, Weissmuller and Bill.

The Mark of Athena
Bythos and his comrades rescue Leo Valdez, Hazel Levesque and Frank Zhang from drowning in the ocean after they defeated the skolopendra. He later interrogates Frank in order to figure out why they were here and whether they could trust them. He later shows up with Frank and both he and Aphros discuss the situation with them. He later agrees to send a group of mer-heroes on a quest to save the creatures trapped by Phorcys.