Arena built with sandstone, which you operate from the outside. There must always be two players, because otherwise the player in the arena will not get any opponents and will not be able to get out. (PvE = Player vs Environment)

It is relatively simple to build. The whole thing is built square and can be built with blocks of any kind. To get into the arena you have to go down the stairs in the main building and press a button there, so that the bricks move apart by means of sticky pistons, and you get into the arena. Another player must always be in the stands to determine the difficulty. I made it so that there is one button each for zombies and skeletons. These are then unlocked with redstone with a dispenser containing the zombie and skeletons respectively. to get out the second player has to pull a lever to get the other into the room containing their reward.

Instructions:

This is what the buttons for the donors might look like:

This is what the Hall of Victory could look like: