The Crossbow is an engineered ranged weapon that allows for easier drawing than a normal bow, thus requiring less stamina.
- For the basic principle, compare: Crossbow (Wikipedia)
Crossbows are a very uncommon weapon in Innworld. So uncommon, that neither adventurer-guild [Receptionist] Selys nor the shopkeeper of a Gnoll Weapon's shop had any idea what Erin wanted to buy as an emergency weapon for her inn.
Cervial had acquired a dwarven-made master crossbow that he put to use during the raid on the Ruins of Liscor. This weapon was a novelty to most of the adventurers that went with him and was meant to ensure their success.
After Cervial's demise, Rags found that very crossbow, managed to repair the apparatus and let the goblins of her tribe copy the design. That resulted in less powerful weapons than her black crossbow, as it was referred to in the series from then on.
Ryoka also couldn't remember having seen a crossbow anywhere in Innworld, aside from Rags'/Cervial's.
Goblin [Tinkerers] under Rags created a few stone-shot crossbows. These had a lot less range and accuracy than a crossbow that used actual arrows, but ammunition was plentiful. Goblins could load them with small stones or even roll clay and dirt into pellets and bake them near a fire until they were hard.
After leaving Tremborags mountain, Rags managed to get better-quality parts and let her [Tinkerers] improve the crossbow designs further. The goblins under her command eventually managed to manufacture more than a hundred crossbows that were capable of firing bolts. Even then, Rags owned her black crossbow which was still superior.
Stan, nicknamed "Crossbow Stan" was a [Crossbowman] who infamously carried around six loaded Crossbows in his Bag of Holding. Where and how he acquired them is unknown, but this had been his trademark style for a long time, since Ceria knew him for it.
Forgotten Wing Crossbows
United Nation Crossbows
Daly and his Bushrangers were hunting with a crossbow that was described as a beast, made almost entirely of wood, save for a few small parts like the screws, sliding mechanism, and part of the trigger.