The Crawling Mountain

The Crawling Mountain is a creature that has gone down in Dwarven Legend as a massive, solitary, and perhaps eldrich creature that was first spotted by the dwarves Anundr son of Eyvindr, Grím son of Gautstafr, and Inga daughter of Ingi. It hasn't been seen since, but once in a while, one can hear its long and haunting call echo throughout the Middleneath Mountains (name subject to change).
Grím was the one to write about it, going into great detail in his journals, of which were found after his disappearance when he was 257 years old.

"Alas, it is most difficult to discribe. Aye, it is safe to say that the Ashkadakh is beyond anyone's ken. Where it came from, anyone can say, but I know that it must have been forged upon the Mighty Smith's Empyrean Anvil. Nothing else could have created such a wondrous creature." – Grím, son of Gautstafr, of the House of Beryl, 5th Journal of Grím, Moonstonesdae, 7th day of the Month of Spinel, 550 3E

According to all three witnesses, The Crawling Mountain looks no different from an ordinary mountain when at rest. But when it gets up to move, the ground shakes and land slides, as if the land all around it trembles in awe of its sheer size. Legs, stony and mountainous like the rest of it, appear from below it and Inga claimed the Crawling Mountain appeared as like a colossal crab with a mountain shell perched upon its back. When it rests, these legs look no different than the cresting spurs of the mountain.
*Names and terms are subject to change.