Akilini was the official sport of Metru Nui, and drew hundreds of spectators for every match. There were pick-up games played on improvised fields all over the city.
In Akilini, teams of three to six Matoran competed to see who could throw more disks through the scoring hoops. Tournament matches were played on the constantly shifting and undulating field of the Coliseum, with hoops mounted along the top of the arena. A special set of chutes was lowered over the top of the Coliseum and players were allowed to use them in maneuvers. The essence of the game was speed and skill, and the physical nature of the sport lead to a lot of fouls.
There were three tiers of Akilini competition. The lowest rung featured play with power level 1-6 disks, the middle rung with level 7 disks, and the best players were allowed to compete with level 8 disks.
The rules of Akilini as stated in BIONICLE: Encyclopedia:
- Akilini matches are played between more than one, but not more than four, teams.
- An Akilini team consists of at least two, but not more than six, players.
- At least one player on each team must serve as a defender. A defender is forbidden to take shots and may only launch disks to deflect the shots of opponents. A maximum of two players may serve as defenders.
- At least one player on each team must be a launcher. If the team has more than two players, a maximum of four players may serve as launchers.
- One point is scored for every disk that passes cleanly through an opposing team's hoop. Disks that strike the hoop are not considered goals.
- Akilini tournament play ends when one team reaches twenty-one goals.
- Disks in play may be retrieved by any launcher or defender from the launching team but may not be recovered by opposing players.
- Disks that leave the playing field are considered to be open to all and may be retrieved by players from any team.
- Players must keep at least one foot on their transport disk at all times. Transport disks may not be launched. Launching disks may not be used for transport.
- Players who go more than one bio outside of the field of play on any side will be considered out of bounds. However, players may go as far above or below the field of play as they wish and still be considered in bounds.
- Players may not make physical contact with a defender at any time.
- Players may make physical contact with launchers, but only after their disk has been launched. Striking, tackling, or otherwise making physical contact with a launcher in the process of making a shot is considered "roughing the launcher" and will cost the offending team one launching disk.
- Players may not use disks from other Metru. For example, only Po-Matoran may use disks made in Po-Metru. (This rule came into existence because players of other Metru often went to Hewkii, a Po-Matoran disk maker, to get Kanoka to play with since his were considered of the highest quality.)