Capture the Flag is a long-time tradition in Camp Half-Blood and is held every Friday. The campers usually play amongst themselves, but when the Hunters of Artemis visit, they face them in a "friendly" match.
The setting of the game is the forest, where the monsters are located and hiding. It's a very dangerous game, but it is beneficial for the demigods because it gives them real life training for the real world.
Two teams are made, and each team has a flag. On each side of the forest, both teams hide their flag somewhere visible, but easily defendable. To win for your team, you need to capture the opponent's flag and carry it across the river that divides the middle of the forest, and acts like a border.
Chiron, the centaur, serves as battlefield medic and referee.
In The Demigod Files, it is revealed that there is a Capture the Flag jail. Captured opponents can be placed in the jail and aren't allowed to leave unless freed by another person from their team. Annabeth and Silena managed to take Percy and Beckendorf away to jail when they played against each other.
According to traditions, whenever the Hunters visit the camp, a "friendly" game of Capture the Flag game will be held. As of The Titan's Curse, the Hunters had won the last 56 games in a row (much to Chiron's and the campers' dismay).
- The creek is the boundary line.
- The entire forest is fair game.
- All magic items are allowed.
- The flags must be prominently displayed and can have no more than two guards.
- Prisoners may be disarmed, but may not be bound or gagged.
- Killing or maiming is NOT allowed. The punishment for breaking this rule is loss of dessert (for one week), as revealed in The Lightning Thief.
- Guards aren't allowed to stand within ten yards of the flag.
There have been only four known Capture the Flag games, once in The Lightning Thief, once when the Hunters of Artemis visited in The Titan's Curse, and twice in The Demigod Files, though one of them is referred to and not much information is given.
After Percy doused Clarisse in the toilet, Annabeth exclaimed that she wanted Percy in her team in the Capture the Flag game later on, probably because she knew that Clarisse would want revenge, thus leading to an unexpected victory by Percy.
During this game, the two teams were Percy, Athena, Apollo, and Hermes (the latter were the two biggest cabins) VS Dionysus, Demeter, Aphrodite, Ares, and Hephaestus (all the other cabins with campers).
Percy was put on border patrol near the river, but he was actually a diversion/bait for Clarisse and her cabin planned by Annabeth (the captain) earlier. The plan worked and Luke grabbed the flag. A hellhound appeared after the game ended and attacked Percy, leading him to be claimed by Poseidon.
When the Hunters of Artemis visited Camp Half-Blood, as per custom, a friendly capture the flag game was played. Team Camp Half-Blood comprised of the members that were at camp during that time, Percy, Thalia (they were co-captains), Charles Beckendorf and two other Hephaestus members, a few Ares campers, the Stoll brothers (Hermes) and Nico, who was also from Hermes, but was undetermined at the time because no one knew he was from Hades, and the Aphrodite cabin also participated.
Camp Half-Blood took the West Wood while the Hunters took the East Wood, it was agreed that Percy would play defense at Zeus' Fist, while Thalia would go and capture the flag. Thalia sent Silena as a decoy, while she led the main party, Percy saw an opening and ran for the flag, he managed to grab the flag and ran past Bianca who was the guard. Thalia got to the flag after Percy to find that it was gone and was very angry, meanwhile Zoë also managed to get their flag and when Percy was one meter away from the river she passed and tripped him in the process. The Hunters won for the 56th straight time, Thalia and Percy were blaming each other for the loss when the Oracle came outside and gave Zoë a prophecy.
Before the following game, it is mentioned that the Hephaestus cabin captured the Ares Cabins flag, with the help of Percy.
Beckendorf was dragged into the Ant Hill by a troop of Myrmekes and Percy, Annabeth and Silena had to save him. At the end Annabeth asks Percy out for the Fourth of July fireworks by saying "see you at the fireworks?"
While there isn't an actual game of capture the flag, when Hazel is describing how the War Games are played at Camp Jupiter, they equate it to capture the flag. Percy has no memory at the time, but knows he likes to play capture the flag.
During the movie Annabeth and Percy duel at the site of the red flag (after Percy accidentally finds it). Annabeth defeats Percy, but Percy then goes to the stream and the water heals his wounds and energizes him and helps him defeat Annabeth and all of the rest of the red team. This is inconsistent with the book.