alien world tournament

On the planet of Valhalla, there is a cult that prizes strength above all things. They hold a tournament every one of their years. People who pride themselves on their fighting prowess regularly come to compete.

The battles are all unarmed, with any humanoid species allowed to compete. It is held in a huge coliseum like ancient Greece, but with a wrestling ring like a wrestling arena. Knockout, submission, or a 5 second pin will win. Killing is allowed, but all precautions will be taken to prevent it using their advanced medical science.