You must be registered for see images
It seems Mei isn't useless after allthat first pic is kind of... well.. hot lol. pun intended
It is just chakra. Like Megan said it's the same exact thing as other ninjutsu. "Well how does Sasuke and Itachi fire jutsu clash, u cant burn chakra!!!"
It's made of Nokia phones.
You must be registered for see images
Chakra that becomes solid. Plus think about it, Mei's Solid Mist uses chakra so it isn't that hard to imagine chakra melting chakra