A curious interplanar liquid that holds visions of other worlds.

You reach inside the chest and pull forth a plain glass jar of translucent gray material. Strange, colorful images pass through the material as if it were displaying the dreams of another world. - Battle at Blacklake (RPA-ADV1) 

Gray matter is a viscous liquid first seen contained within a simple glass jar, the prize within the durgolium chest guarded by the Ogre Tog.

It displays dreamlike images in its form.

Upon exposure to the outside world, a strange event takes place;

As the chest pops open, the earth quakes and the sky crackles with strange purple energy. For a moment, you hear the screech of bats, and you smell a briny sea. - Battle at Blacklake (RPA-ADV1)

Tucking it into a chainmail sack made of the same metal from Tarik ends the phenomenon;

You place this curiosity in Tarik’s durgolium sack. Immediately, earth and sky are still. - Battle at Blacklake (RPA-ADV1)