Mul may have once been referred to as half-dwarves, but no one would call them that these days…unless they wanted to mortally insult dwarves.
The ancestors of the mul were definitely dwarves who were captured by the armies of Gristamere in the wars before the First Conclave of the Seven Kingdoms. Hobgoblin breeding and experimentation infused human and possibly hobgoblin blood into them, creating powerful creatures that were, literally, bred for war. Because they were difficult to guide in battle, however, most mul were not pressed ino hobgoblin armies. (Some say that the hobgoblins didn’t need another race to rival the bugbears in irritation level.) Most ended up as slaves, specifically pressed into service as gladiators.
There is strong evidence that muls were also bred to specifically enrage and weaken dwarven morale. The word Mul (pronounced mool) derives from a goblin word meaning “bait”.
Mul are tall and powerfully built. Unlike their dwarven ancestors, they are completely hairless (furthering the insult to dwarven-kind), but their tenacity and stubborness definiely reflect a dwarven nature. They have become a race that breeds true, like half-elves and Urku.
Mul were officially freed under the treaties signed during the time of the Seven Kingdoms, but many chose to stay with their former masters, knowing no other life. Following the Second Witching War, the muls remaining in Gristamere were re-enslaved. Dwarves didn’t make the situation any easier for those muls who chose to leave their previous homes. Dwarves find muls awkward at best and repellant at wost. For their part, the muls find the dwarves condescending and their revulsion ill-concealed.
The future of the muls is uncertain. Many spurn the hand that dwarves have offered to them and the “safety” of life among the hobgoblins to carve their own paths as Adventurers.