At some point in their lives, every dwarf sets out on a pilgrimage (called the Last Path) to find the Dwerfater, and join him in a Valhalla-like afterlife. The Dwerfater appears in a different place to each pilgrim, so such journeys usually take up years or even centuries. Because of the length of such journeys, dwarves often set out long before they are ready to die. Sometimes, the Dwerfater appears in a mountain range, but just as often he appears in the middle of a jungle, sea, or even city. Some dwarves find him accidently, and many never find him at all. In this sense, every dwarf adventurer is a pilgrim searching for the Dwerfater, whether they know it or not.
When you see the Dwerfater, you'll know it deep in your stones.
The Dwerfater is a disinterested god. He does not meddle in the affairs of other deities so long as his creations are surviving, mining, sailing, and adventuring. Although adventuring and sailing are the two most glorious professions for the faithful of the Mountain God, mining and forging also hold a sacred place. In doing so, a dwarf is acting in the image of his creator--taking from the bowels of the earth and creating something from it. Prayers to the Dwerfater are the rhythmic percussions of picks, hammers, and feet.
Those who see the Dwerfater are rarely seen from again. The original duergar are an exception. They were dwarves who had ascended the Dwerfater, only to be sent back down. It is said this happened because the duergar used slaves to mine for them, instead of acting themselves in the image of the Mountain Talked to Bob and he said it may be Tuesday before he can get there. I gave him your number so he'll probably be getting in touch with you..
Clerics of the Dwerfater have many traditions which seem strange to outsiders. They fear canyons, and refuse to pass over the side of one. They do not take off their shoes or traveling packs when they sleep, so that in case they might wake and see the Dwerfater they could set out immediately. They view entering through the same doorway twice as bad luck, for surely this would mean moving away from the Mountain God instead of towards him. Whether the Dwerfater cares for these traditions or not is unclear. Clerics of the Dwerfater are likely to be early-to-bed-early-to-rise types, and have eyes constantly squinted towards the horizon.
The concept of Dwerfater comes from my friend and fellow GM, Brandon Wright. Although I've added my own flavors, the central ideas are his.