Drakon

Drakons, (Ο Δράκων in Ancient Greek, not to be confused with Dragons) are giant, serpent-like creatures several millennia older than dragons. They were first mentioned in The Sea of Monsters and are later seen in The Last Olympian.

The Sea of Monsters
Luke sent Percy, Annabeth, and Tyson to be eaten by a drakon that was on his ship, the Princess Andromeda. He later threatened to have Agrius fed to it after learning that the Golden Fleece had slipped through his grasp.

The Battle of the Labyrinth
An Aethiopian drakon had been in the cargo bay of the Princess Andromeda.

The Last Olympian
A Lydian Drakon was sent by Kronos to defeat the demigod forces protecting Mount Olympus. This drakon could only be killed by a child of Ares, but because the Ares cabin had refused to fight, the drakon plowed through the Olympian forces and killed a large number of centaurs. It wasn't until Silena Beauregard was killed after charging the drakon in Clarisse's armor that the Ares cabin joined the fight. Clarisse charged the drakon in a vengeful rage without any armor and only her spear as a weapon and kills the drakon in the Battle of Manhattan before she received the Blessing of Ares.

Leo Valdez and the Quest for Buford
A drakon appears in the Camp Half-Blood forest, while the Maenads are rampaging through the forest. It is ripped apart by the Maenads.

Abilities

 * Some breathe fire, though most don't.
 * Some spit acidic venom.
 * All have extremely hard plate-like scales on their skin.
 * Most can paralyze you with their eyes.
 * Extremely hard to kill (the Lydian drakon was able to withstand several javelins to the mouth).

Sub-species

 * Aethiopian drakon
 * Lydian drakon
 * Theban drakon