The duels between the Birdmen (or Grakg'ria in native tongue) of Melchylia has few and very simple rules: 'Fly at a high and deadly altitude with a distance that prohibits physical contact between you. But stay visible to each other. The one who first falls to his/her death due to exhaustion looses the duel.' (Obviously!) It is a a long and painful process since it sometimes can take days before someone gives up.