Escotarox, the Shadow
The slate grey dragons of the Neitherlands have evolved to almost disappear into their surroundings, like shadows in the dark. Their wings are too heavy for flight, and so they scurry along the rock bank with speeds exceeding comprehension.
While most slate grey dragons are small, no larger than a mid-sized boulder, Escotarox, the Shadow, can expand or shrink his size to suit his needs. Wayward explorers report only discovering they were climbing his expanded, mountainous back when they realized the shaking wasn’t an earthquake, but Escotarox’s slumbering breath.