You give your stunned acquiescence, and for weeks you watch as Algard and Kragg have loud but enthusiastic disagreements over the fundamental nature of magic, and day by day the largest Rune you have ever seen is constructed out of layer after layer of ground diamond. Apparently Gazul's realm is metaphorically below the mountains, and diamonds are born literally below the mountains, so there's a conceptual link between the two. Unlike other Runes you've seen made, this one doesn't snap into a new nature once complete; the air chills in an instant as a blue fire you can only see out of the corner of your eyes burns its way slowly through the diamond dust, leaving it transparent and utterly invisible unless you can spot how light bends as it passes through the Rune. Then, to your surprise, it is not installed in the tower. It is, instead, buried in the deepest point of Karag Nar, right on the boundary between where mountain ends and where the rest of the world begins. It's also directly under the tower, measured to within a hair, and over the course of weeks a steel beam is built from the tower to the Rune, displacing several rooms in the process and leaving a rather forbidding steel pillar glowing with a faint blue light in the center of your entrance hall.