Uglib

The Uglib was an impressively tough donkey bred by the dwarves and used widely in dwarven and gnomish mines. They sold for 35 gold pieces in most places, but dwarves and gnomes sold them at a 10 gp discount to each other.

Description
The Uglib was a very ugly beast, having beady eyes, mottled tufts of hair, and a stubby tail. Some specimens of the breed even grew bone spurs, though these were harmless. Behind this unfortunate appearance, these creatures were far tougher and stronger than the common donkey and especially stable on their hooves.

History
So common were these animals among the dwarves and gnomes that magic portals were even created for the sole purpose of transporting them from mine to mine.