Berserker's Planet

A party of illegal big game hunters lands on a preindustrial human colony planet with a warrior culture and religion, and decides to watch a global gladiatorial tournament to the death, where combatants vie to be rewarded for a valiant death with a seat near their warrior god in his feasting hall. However, the religion is secretly manipulated by an ancient Berserker AI dedicated to the extinction of all life, which has staged the tournament as a lure in order to capture a visiting starship and escape the planet to destroy life on more planets.