Under the Twisted Weirwood Tree

It's Purge Night in Westeros. As it so happens, it's also Roose Bolton's turn to host the annual New Conquerors fundraiser. Sansa thinks that's an excellent reason to skip the festivities. Tywin thinks not showing up would be seen as a sign of weakness. What could possibly go wrong? Westerosi Purge AU with some Orwell thrown into the mix for good measure