Vis Crystal

A metallic crystal that often appears in cube-shaped deposits. It is exceptional at storing magic, making it ideal for use as a "battery" for spellcasters and mages. It is well known for being the highest capacity magical energy storage material, but it is much more fragile than some of the other options- as such it's not often used by combat mages or embedded into armour/weapons.

Type

Stone

Rarity

Relatively common

Color

Shiny, iridescent red