Donnerglass

There is something elegant and terrifying about the power of the storm being trapped in some small shard of glass. Look at how it sparkles whenever a storm arrives - if we are not respectful, the lighnting will break out again to struck us down.

Donnerglass is the dark blue, almost black substance left behind when thunderstorms hit the surfaces of the Donnercliffs. It holds residual energy of the god Donar and is believed to be a small shard of their actual power.
The glass is very inflexible and will shatter under enough pressure. Shattering a Donerglass shard will result in a bright flash and the shards being propelled by a stronger force then was used to cause the breaking. It becomes malleable when hold into a flame for a short while and be very slightly deformed. Despite being easily to break, it seems to be completely resistant to weathering.
Although usually found ath the Donnercliffs, there are small deposits of Donnerglass all over the Chaukenlande. Most well known is a large column made out of Donnerglass that supposedly stood on top of a mountain for centuries.

Uses

Uses in Weaponry

Despite being relatively easy to break, several smiths have experimented with forming weapons and armor out of this material. It does not work well as blade, but is an interesting material to use as simple plating on top of leather armor. Despite the extra protection, shattering such a plate will shortly blind the opponent, making it an interesting defense.
Using the Donnerglass as arrowtips also proves devestating - the arrows will usually shatter on impact, causing terrible wounds as well as blinding and disorienting the enemy due to the mighty flash.

Uses in Runemagic

Some ancient texts discovered by local Runesmiths describes how to actually make the Donnerglass malleable enough to inlay runes with the material. With some magical power and carefully applied strong heat from a forge, the glass can become of a resin like viscosity and even be divided. It will keep the new forms after cooling off.
Runes inlayed with donnerglass seem to add to the force of an effect. Especially if the effect is to cause speed or impulse, the affected will build up speed quicker and achieve forces higher then usual. Some Runesmiths have started to enhance weapons for the warriors of Troumwarft.