At first, he is a baby dragon. Peleus soon grew large enough to encircle Thalia's Tree. Peleus is snake-headed with copper scales and yellow eyes.
Peleus is a tame, domesticated dragon that is loyal and fond of the campers, as Annabeth has been shown petting him in the past with no ill response from the dragon. However, Peleus seems to be fiercely dedicated to his duty given that he's always around the Golden Fleece. Percy Jackson once feared that he would attack Rachel Elizabeth Dare on sight, implying that Peleus is violent toward strangers. However, given that he didn't attacked her, it's safe to assume that Peleus is intelligent enough to distinguish an ally from a foe.
Since Percy, Grover Underwood, Annabeth Chase, and Clarisse La Rue brought back the Golden Fleece from Polyphemus' Island to put on Thalia's tree, they had to find a suitable guardian. Peleus, a baby dragon at the time, was chosen. Chiron and Argus fed and looked after him until he was able to care for himself and the Fleece.
When Rachel Elizabeth Dare forced Blackjack the pegasus to fly her to Camp Half-Blood, Percy was worried that she might get attacked by Peleus due to her being a mortal. However, the dragon did not attack her, possibly under orders from the gods or he knew of Rachel's importance as the future Oracle, and realized that she was not a threat.
When Annabeth is giving Piper McLean a tour of the camp, Piper sees the Golden Fleece and thinks it is a decoration or a forgery of the original (being that she is in a Greek camp) until she sees Peleus, and realizes it is the real thing.
- Peleus may be named after the father of Achilles.
- Peleus was the son of Aeacus, king of the island of Aegina.