A Legion was made of five cohorts, each one made out of six centurias of eighty men. Like in Camp Jupiter, the most prestigious one was the first, then the second and so on. Normally the Centurion of the first Centuria commanded the whole Cohort.
As recently as the 1980s the Fifth was accounted the best of the five Cohorts, but that all changed when Michael Varus, a legionnaire of the Fifth and senior Praetor led them to disaster in Alaska, losing the Legion's eagle and most of their Imperial gold weapons. He had thought he could complete the Prophecy of Seven, despite being warned that it was too early. Nobody knows what happened as everyone either died or went crazy and refused to talk about the experience.
Jason Grace had gone a long way towards restoring the Fifth's status by his leadership through the Titan war, but his unexplained disappearance destroyed all their gains and they went back to being a disgrace. Percy Jackson reverses the trend again in The Son of Neptune with Frank Zhang and Hazel Levesque, by bringing back the eagle and the lost weapons. Percy Jackson rescues the camp from Polybotes and is made praetor for his heroic actions, bringing respect back to the Fifth cohort.
When Percy arrives at camp and was to be placed with a group, Frank stands up for him, but because he is on Probatio, he isn't allowed until Hazel stands up and agrees to be his representative. Reyna agrees and Percy becomes part of the Fifth Cohort and learns they are the weakest group at camp. Percy helps turn the tide during the camp's War Games, where the Fifth manages to take down the enemy fort by themselves.
In Alaska, Percy retrieves the Legion's Eagle and destroys the ghosts of the Fifth Cohort (the ones who went on the doomed expedition to Alaska in the 80's). Frank frees Thanatos and along with Hazel, defeats Alcyoneus. The trio gather the lost Imperial Gold weapons and rush to Camp Jupiter.
The Fifth Cohort is once again restored to glory, and defeat the monstrous army attacking Camp Jupiter. Percy slays Polybotes in a one on one duel, by smashing his face with a Terminus statue, and is raised to Praetor.
- Dakota (Senior Centurion)
- Hazel Levesque (Centurion)
- Frank Zhang (Praetor)
- Percy Jackson (Former Praetor)
- Gwendolyn (Former Centurion)
- Jason Grace (Former Praetor and Centurion)
- Michael Varus (Deceased, Praetor)
- Bryce Lawrence (Deceased)
- The Fifth Cohort has housed four out of the five known praetors: Jason Grace, Percy Jackson, Frank Zhang, and Michael Varus.
- The four are also all the known male praetors.
- Despite being considered the worst cohort, the Fifth Cohort has housed four of the seven of the Great Prophecy: Percy Jackson, Jason Grace, Frank Zhang, and Hazel Levesque.