What is the meaning of the phrase "Faustian deal" in the following paragraph: "On the subject of Osama, he (Musharraf) is so slippery you want to lock him in a room with the muscle-bound Armitage," Dowd wrote. " The Pakistanis are at the heart of the Faustian deal the Bush administration has made. The justification for invading Iraq was that they couldn't allow a dictator who might be harbouring terrorists to stay in power. But their great ally in the war on terror is Musharraf, a dictator who appears to be harbouring terrorists, including the one we (Indians) want most."