Thread:Whovianfan/@comment-5038193-20160605231340/@comment-6945486-20160605231749

The Power Stone from guardians of the galaxy. It was used by Ronan once to attach to his hammer to make it stronger.

http://vignette1.wikia.nocookie.net/marvelcinematicuniverse/images/9/98/Power_Stone-Clean.png/revision/latest?cb=20150101230630