Azantium

Azantium (アザンチウム) is a mineral found in Tortus.

Description
Azantium is a jet black ore that is considered to be the hardest substance in the world. Even a light coat of it is enough to withstand most attacks.

Currently the only things capable of breaking Azantium is an object that is also made of Azantium, and the magical flames of a dragonman.