In the western peaks, in a valley that appears on no reliable map, lairs Mitasslus, an earth dragon of immense age. His scales are the color of weathered sandstone; his eyes hold the patient darkness of deep caves. He has been here since before the Postronamas built their pillars, since before humans came to Clueanda, and he will be here long after.
Mitasslus guards a passage to the Underrealms, one of the deep gates connecting the surface to the vast cavern systems below. He doesn't guard it because he was asked to. He guards it because things come up through that gate, and he has decided they will not get past him.
The dragon is neither good nor evil by mortal reckoning, simply territorial beyond any negotiation. He won't attack travelers who keep their distance, but anyone who enters his valley uninvited will be buried under half a mountain. He hasn't spoken to a mortal in centuries; most believe he's incapable of speech. He is not. He simply doesn't see the point.
Occasionally, Mitasslus emerges to sun himself on the high cliff faces. When his silhouette appears against the sky, caravans on the northern trade routes know to detour. Locals leave offerings at the valley's mouth, not worship exactly but acknowledgment. The dragon ignores them, but the offerings are never disturbed.