Adamantine

This metal is famous for its incredible hardness. An adamantine object has immunity to all damage except adamant damage, and -- unlike other objects -- it doesn't have vulnerability against adamant damage.

White adamantine (called mithral in Elvish) is found in the heart of the world, whereas black adamantine (called ghalvorn in Elvish) is found in the hearts of fallen stars. The two varieties are mechanically identical.

Adamantine Ammunition (Bundle) (Rare): Attacks with this piece of ammunition deal adamant damage instead of mundane damage.

Adamantine Weapon (Rare): Attacks with this weapon deal adamant damage instead of mundane damage.

Adamantine Armor (Very Rare): When you take mundane damage while you wear this armor, you can reduce that damage by 1. To benefit from adamantine armor, you must not be incapacitated.