When hosting games I like to make sure everyone is having a blast and if one side is just obliterating another I like to introduce random threats to throw everything "tits up". Harpies make for great game hiccups or stabilizers and can really throw a wrench in a Commander's game plan when they appear. So if a game is getting too one-sided, throw in a couple of these "birds" in the mix and throw everything off-plan for a bit. Grab the rules here.
Now them are some birds of prey!!