I just took a look at the walkthrough:
Back Hall Click on the chest to play Raven's Hunt. Directions are in the game and you can click on the large reset button to choose Hard or Easy.
When you accumulate 2,000 points, the chest will open.
A bottle of anti-venom is automatically added to your inventory.
Enter the Hall behind the chest.
I can't tell from reading this whether or not the chest should have opened, or if the chest opens when you back away. Maybe someone else familiar with this game will know for sure. You could try backing away and see if anything happens, although hopefully you have a saved game right before this part so that you could replay it if necessary.
Sorry I don't have a definitive answer to your question.
I did find a neat tip from the developer about an easier way to win this game:
If you are having trouble beating this game...
Simply keep pressing RESET button until the board shows twice as many ravens than snakes - play that board... then once board is cleared... keep pressing RESET until there's twice as many ravens than snakes (it's actually too easy once you play it this way) - eventually you will beat it.
Once in a while a board will play its self out without even getting a chance to move... however this should be rare and sort of the trade off for being able to hit reset so many times until you get a board in your favor.