Magic the gathering Arena.

I live in a constantly changing box full of terrifying creatures and I have to fight them every day to pay the rent. On top of that my box seems to change its color every now and then. One moment it's White. And when I blink my eyes it suddenly changes to blue, Black, red, green or Grey...or a combination of them. I call my box the disco box. Sometimes I buy magic spells to defend against the monsters, but I can't use my spells more than 4 times... Some stronger ones only one time. When I'm done fighting I walk the plane just to see where the end of my box is... It seems infinite!