Greenish Metal Shard  

 

My guess is that the original must have been crystallized Greenmist, which in its gaseous form was what drove the Shissar to airless parts of Luclin,its like nerve gas from what I understand,in its effects and such, though it is a lot more viable, in that it could spread over a wide area so fast,since most nerve gases are not viable for widespread usage because they don't spread through air very well, so maybe more like a virus so pretty durn powerful I'd say, especially if there was some huge 2 handed sword made from it.