Boy, I can't stop being evil in RPing!

Right now I got everything lined up to:
1.  Poison my allies, since they're about to eat some poisoned hog roast.
2.  Demolish the only exit out of the mountain pass.
3.  Butcher a group of reinforcements a leaving-player has left me (and then steal his horses)
4.  Enter into a deal with the opponent to save my own skin once the deeds are done.
5.  Send the heads of my allies to their respective nations.

And yes, the GM has already said this is okay to do.