If you start a game of Raven and then leave your computer alone without touching either keyboard or mouse for about an hour or so, then the puzzle *should* auto-solve and the antidote will appear in your inventory.

However, several members have reported this skip feature not working for them. But it's worth a try.

Otherwise, keep starting a new game until you find one which has many more ravens than snakes and so will be likely easier to win. The ratios do vary from game to game.