Since this roleplay does not have an actual lore, you do not have to follow this. I invented this lore for the example battle in the thread of Planet Zero.
Overview
People from all over the universes are disappearing. A planet in the Null-Universe, an untraceable universe where all the bad things are kept, is alive again. This planet known to people by many names, however its origin is not known. A planet completely barren of all life, but a large building survives. This building is known as the Main Hall. Portals are opening up from all over the planet bringing in new people. The ring master is unknown but once you enter the Main Hall you cannot leave until you are the last one. For those who don't wish to fight, they are forced through a type of mind control. The technique is unknown but it starts with 3 chimes, after that you go blank.
Journal of Urahara Kisuke
Main Planet -
Over the days I have found that the planet is full of dangerous traps, unknown species which roam around the land, It almost appears as someone is using us for their amusing...
The planet covers several elements around it's giant surface, darkness never seems to fade, it's nothing if not a planet where you fight for even the basics like food and water.
Arena Planet -
Two times so far it appears we were summoned to another location, due to the huge difference in the environment I'm assuming it is a whole new planet, in which it seems we are forced to fight each other one on one until only one remains as the victor.
Encounters -
I have located several others who appear to be in the same position as I am in, in a place like this a man turns off their interests and would ally with anyone to survive easier.