Basilisks are snake-like mosters. Their name means "little crown".
When the giant Polybotes walks past R.O.F.L., the goddess Iris' shop, the basilisks appear. Iris does not let them in and defends herself against the army with her rainbow. In retaliation, Polybotes releases three basilisks out of his hair and they circle the shop, not letting anyone leave or enter. Frank Zhang manages to kill them with some help from Gray, a gift from his father, Mars.
Polybotes summons basilisks to kill Percy at the bottom of the ocean when Jason Grace and Percy Jackson are confronting Kymopoleia. Percy slashes through a few of them, but most of them are out of reach and they refuse to listen to Jason. Then, Jason summons a lightning bolt which kills them and he tells them they should look at him when he talks to them.
They are little green snakes with an expandable collar of white spikes around their necks. They can breathe fire and their touch is poisonous. They can be as long as a man's arm.
- They are able to spit fire and are very poisonous. When one simply touched Frank's bow, it disintegrated.
- In myths, they were said to have the power to cause death with a single glance, however this does not seem evident in the The Son of Neptune.
- The basilisk are also called "KING" because it is reputed to have on its head a mitre or crown-shaped crest.
- Weasels are deadly to them.
- The giant Polybotes can make them fall out of his hair.
- "Basilisk" in science refers to Basiliscus, a South American genus of lizard containing four species.