It's the stone to rule all stones! (not really)
The Atturnel was found by Tenoss in the mountains of Titoneh's Arm (see my map to find out where this is). It was with the help of this stone that the Ashtains were able to defeat the Magicians of Teynon.
The Atturnel has many different "abilities":
It can judge a man's heart and show if it is pure of corrupt. Normally the stone is a clear teal, but when used by a corrupt person it turns blood red. Attensie told Tenoss to use the stone on his soldier's armor. The stone would remain teal if the soldier believed Attensie would protect him, but would turn red if they stopped believing. As long as a soldier believed, the magic of Teynon could not harm him, but the moment belief was lost, the magic could kill them.
The stone was set on the front of soldier's helmets. They couldn't see when/if the stone turned, but others could and could try to make them believe again. On Tenoss' personal guards, the stone was the "clasp" for their shoulder plates.
A chance finding of the stone before Tenoss' rule was by his predecessor; Sanah the Conqueress. The stone was used to make a suit of armor for Sanah which she used once in the final battle with the Zarack. The armor was impenetrable and unbreakable. It looked like teal colored glass and a silver star was crafted into the breastplate. Even the ring mail under the plates was made of Atturnel. The suit itself was strangely light and hardly hindered Sanah's fighting. The armor was never used again and is lost somewhere in Ashta. It was not destroyed and did not rust away, it's still there somewhere...
One city was built with Atturnel in it's walls. TalizoreTovKineth. The builders ground the Atturnel and used it for mortar. The Atturnel caused the stone to become a solid piece of rock with no cracks. On the outer walls they covered the lower portions with the Atturnel mortar to give it extra strength. While building they discovered that the Atturnel, if it came in contact with a certain liquid, could catch things on fire. As an added defense for the city, they crafted pots of the liquid that could be poured onto the lower walls. From there fingers of electricity/lightning would reach out and consume any enemies that dared too close. This also destroyed any possibility of ladders and towers as they would burn before they got close enough.
When turned into mortar, the stone lost all color and became white.
Because of its ability to judge a man's heart, many leaders carried a piece of the stone with them. They used it to judge someone before making a pact with them.
The only nations who know of the Atturnel's existence are the Ashtains and later the Ashvat. The stone was a closely guarded secret.
The Atturnel is Attensie's stone.
So there you have it. The prize resource of the Ashtains
Did I miss anything? Any questions?