Leonidas was a historian.
He took Bernice Summerfield to Ruth Leonidas and gave her answers. He had lost his wife, as she believed she was a different person. When he went to the Layer of Poseidon he helped to find the truth. (AUDIO: The Temple of Questions)
He later tried to impress Benny by making fish finger sandwiches, and was told about the hierophants by Craisus. He accompanied Benny to a 27th century building that appeared in what she thought was ancient Greece. He grew attracted to Benny. He later was rewritten into a hierophant called Trellus. (AUDIO: Private Enemy No. 1)
In a simulation created in a museum about Benny's life, he talked about their little family. This simulation later helped him to defeat a horde of the enemies created from her memory. (AUDIO: Many Happy Returns)