Today I came up with a type of weapon for one of the cultures in my WIP, but not being an expert in combat I'm unsure as to whether it would really be practical, or how such a weapon would be used. Essentially it's a double ended knife, gripped by a hilt in the middle with a blade on either end. The fore-blade would be metal (usually steel.) and the aft blade would be made from obsidian. The time period is roughly medieval. I have a few ideas for how it would work be am not sure. Any ideas?