Lysas was the chosen one of Pan, being tasked by the god himself to spread the word that, "The great god Pan has died." Even though he refused to believe this, he spread the word to the world in Ephesos.
Lysas is mentioned when the members of the quest for Daedalus find Pan in his cave in the Labyrinth. They are told about how the god had tried to tell the world about his death, and wanted to fade away, but the satyrs refused to believe this. He then tells Grover to do the same as Lysas.
Lysas is portrayed by Pan to be like Grover, who is brave, good, and a true satyr.