The rarity of Pact of the Wurmblood is Mythical, and been equipped it takes a “Bundle” slot. At this moment the item is available for trade.
Pact of the Wurmblood is a skin for Dragon Knight. The skin was added to the game on July 8, 2015, it was created by ChiZ.
Pact of the Wurmblood is currently one of the most popular skins, but it is rarely seen in the game due to its high price.