The Eagle of the 12th Legion is the eagle standard that was given to the Twelfth Legion, supposedly by Jupiter himself, and is the symbol of Camp Jupiter. Julius Caesar nicknamed the Legion "Fulminata," meaning "armed with lightning," because of the Eagle's incredible ability to strike lightning upon the battlefield.
The Eagle was given to the 12th Legion by Jupiter, who imbued it with massive power.
It was first lost during the Jewish rebellion (approximately 70 A.D.) and its loss was a massive disgrace. Fortunately, it was recovered later on.
Later, the Eagle was lost a second time in the 1980s when the senior Praetor of the Twelfth at the time, Michael Varus of the Fifth Cohort, ignored the advice of his augur and lead an expedition into Alaska, thinking to complete the Prophecy of Seven. He lead the Fifth Cohort to Alaska where they encountered Alcyoneus. The resulting conflict ended with the virtual destruction of the Cohort and Alcyoneus seizing the Eagle. At some point he placed the Eagle on the Hubbard Glacier to be guarded by the undead legionnaires there. Due to this loss the Fifth Cohort was disgraced and became the unpopular Cohort of the Legion. The Fifth Cohort was also said to have bad luck tied in with the loss of the Eagle.
The Eagle was kept in the ice covered imitation of Camp Jupiter on top of the Hubbard Glacier where Thanatos was being held captive. During the battle after being ambushed by the shades of the long-lost legionnaires, Percy Jackson, protected by his hurricane, seizes the standard and uses it to keep the ghosts from attacking Frank, who was releasing Thanatos. Percy also holds the eagle in his other hand when he destroys part of the glacier upon being overwhelmed by number ghost legionnaires fighting him. When Hazel Levesque and Frank Zhang return, they find Percy leaning on the staff with the golden eagle on top.
During the battle on the Field of Mars, Percy uses the power of the eagle to destroy hundreds of monsters in the center of Polybotes' army, after which he hands it to Dakota. After the battle, the eagle is temporarily placed behind the Praetors' tables in the mess hall. It has presumably been restored to its normal place in the principia.
- The early Legions of the Roman Republic also used one of the following symbols other than the eagle: The boar, minotaur, wolf, and bear. The eagle only became the standard of the legions after the reformation of the army by the Consul Gaius Marius.
- Each Legion of the Roman Empire was given a symbol which were imbued with the powers of different gods. The Eagle was the physical representation of Rome's power and prestige and accordingly, it was considered a very sacred duty to guard the Eagle. The Romans would sacrifice their lives to protect these symbols and some were melted down or destroyed instead of being handed over to the enemy. Only the Twelfth Legion's Eagle has been seen in the series because they are the only known remaining legion.