Uru

Uru is a magical magical substance that comes from Asgard. It was used to make the mystical hammer Mjolnir for the thunder God Thor.

The element can fly, travel through space, open portals through space, and has a semi-consciousness. It will only allow it to be wielded by those the weapon deems worthy of it. It can also enhance the power of the holder's abilities, such as Thor's control over the weather.

Background
In the comics, Beta Ray Bill's hammer Stormbreaker is also made of Uru. However, in SS undefined it is simply an illusion. The unseen Heimdall and Odin also have Uru weapons.