
QUESTION: If a donkey is the king of the beasts of burden, then who (what) is the emperor? (And yes, this is a FS question :p )
Hint 1: We're talking about an actual beast of burden, detailed in a FSR source discussing (among other things) beasties in the Known World.
Hint 2: It is an old Urth animal, with a write-up based on real world research and facts.