When you planeswalk to The Pit, each player creates their choice of a 3/3 white Angel creature token with flying or a 6/6 black Demon creature token with flying, trample, and “At the beginning of your upkeep, sacrifice another creature. If you can’t, this creature deals 6 damage to you.”
Whenever chaos ensues, each player sacrifices a nonartifact creature of their choice.
To resolve the first ability, starting with you and proceeding in turn order, each player chooses which creature token they're creating. Then all creature tokens are created and enter the battlefield at the same time.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.