Martha

"Don't be discouraged when you read it, dear. He does have your possibilities at heart."

- - Martha to Percy

Martha is a snake that was caught by Hermes though she is not a Monster. Demigods and gods can hear her in their heads. She is immortal always seen with George.

Description
Martha is constantly scolding George for whatever he said. They live on Hermes' Caduceus. When it is a phone, she is on the antenna and also becomes a pen when their costumers receive their packages to sign their receipt. She is kinder, firmer, more understanding and more serious than George and often soothes Percy when he's confused.

The Sea of Monsters
She makes her first appearance when Hermes visits Percy near the lake in Camp Half-Blood and Martha is with him. She gives the Thermos of winds as a gift for Percy. She is constantly scolding George for saying things that are out of the conversation and for teasing Percy. She appears the second time with Hermes to deliver a letter from Percy's father, Poseidon. She advised Percy to not be discouraged when he reads it.

The Last Olympian
Hermes arrives in Olympus to deliver a message. Martha and George with him. When Percy says something that angers Hermes and tries to punish him, Martha and George comes to the rescue and whisper to Hermes that Percy has the curse of Achilles.

They were with Hermes also at the end of the Second Titan War, when Luke had died. She was whispering, "Luke, poor, Luke". They were silent when Hermes talked to Percy.