Season three of HBOs Game of Thrones reached a particularly bloody climax in 2013, but it looks like the shows fourth season will try to top its body count. HBO has released a new trailer, portentously titled Vengeance, that opens with lady of the North and mini-murderer in training Arya Stark reeling off a list of people shes planning to kill. Shes not alone in her bloodlust, either: most of Game of Thrones extended cast seem to have revenge on the brain, including mysterious new characters such as Dornish prince Oberyn Martell. …