Killer.io is a multiplayer stealth game that takes place in a house being used for a party. This exciting.io Halloween game has you playing the part of a murderer and competing against each other. You should try to get rid of the revelers in order to avoid being caught. You will be competing to become the most murderous player before the game ends. This will require you to search for hiding places and increase your kill count. You can transform yourself into a sly killer during Halloween!