The 3rd stage of the annual John Van Caneghem Tournament (2007).

Added 4 minutes later

For example, in the Fortress where the Titans are. Build a shop there and experiment. But in a real game, during a tournament, always sell artifacts from the Hero, not from the backpack, so you don't mess up and accidentally trigger a bug, or you'll be caught and..., well, you know what happens next :)