Angryverse/Glass

Glass are one of the three common materials used by the pigs for construction, it would make a great reflective mirror if it wasn't literally so crystal-clear as... well, crystals! and it is definitely the most fragile out of the bunch, as it can easily be shattered just like paper, only crunchier. How the pigs managed to gain possession of such a non-natural material is unknown.

Sometimes glass is replaced with ice, a material that is a lot colder but equally as fragile.