The Chess event is something that so long as you have experienced it once you can beat it every time. If you have some very basic knowledge of how to play chess it makes it a little easier but a run through this event will teach you most of what you need to know.
The main pieces are the King and the Clerics. Only play these pieces if you feel ok with being one of the main players of the game. The goal is to kill the other sides King. Use the pieces besides King and Cleric to clear the way to him. If you can try to kill the other sides healers.
Someone will talk to Medivh which will start the event. You will see all the pieces move in place. You can then talk to a piece and say you want to play that one. If your piece dies you will pop out of it and appear on the steps. You can run down and get into another piece. DO NOT leave your piece before it dies or before it pops you out after the game ends. If you manually leave the piece there is a bug where you will be transported to Curators room and you cannot get any of the loot.
Once everyone is out of their pieces when you win do not open the chest. Let your Master Looter look through the chest and put pieces up for distribution. Once the loot is taken care of you can take your turn at looting your badges from the chest.