The milennias-long forced conflict between immortals, the Game is a series of elimination duels fought free-form between all immortals (utilizing any weapon aside from a bladed weapon skirts the rules). Combat continues, influenced by the Gathering, until there is only one survivor.
Any immortal may challenge any other immortal at any time, so long as the challenged immortal is not on holy ground at the time. To issue a challenge, an immortal must approach his/her target and announce himself or herself and intention to fight. Combat may then begin IMMEDIATELY.
While this is the standard form for a challenge there have been occasions and immortals that disregard or skirt the rules entirely. Shooting an opponent and fleeing, enlisting mortal mercenaries to bring down an opponent and beheading the 'dead' immortal, hunting with a group against a lone immortal, and other violations or borderline violations, while rare, have occurred.