Divinity: Original Sin Enhanced Edition

Brandon in Silverglen will ask you to bring him some Tenebria. This ore can be found in different places - for example, in the cave of the troll king (as well as in the mines and in the Sacred Stone). When you give it to Brandon, you gain the skill of using tenebria without being infected with rot. The same skill can be learned from a book from the magician’s shop in the Sacred Stone (located on the shelf with the same tenebray).