The stately grulm is a large, hairless, semi-aquatic mammal peculiar to the upper reaches of the Umph. They are wading beasts, most at home in the river. They bear their young on the banks in spring, and shuttle nervously between bower and stream until the cubs are old enough to swim. Adult grulm range in size up to eight feet at the shoulder, with a narrow head, lizard-like tail, and thoughtful eyes. The lesser grulm is similar, but it is about half the size, spends far more time on land, and is rarely domesticated.

The grulm is omnivorous, dining primarily on watercress, trout, and the wild black pepper that grows on the banks of the upper Umph. During their time on land in the Spring, they supplement their diet with vermin, apricots, and the autochthonous aubergines and haws of the uplands.

As recently as antiquity, the grulm's range extended as far downriver as Munt. They are moderate creatures who abhor civilization, and so through the ages their range has been steadily reduced.

No one knows when the grulm was first domesticated, but there are representations in the ruins at Munt which are believed to predate the Lonesome Kings. For centuries, the sure-footed grulm has been employed to draw shallow-drafted barges from Narshroum down the river to Eel, bearing cargoes of resin, fleen, hides, and uuer.