What the heck is a "poison-bolted hexbow"?

... The ink on the Noxian and Demacian armistice had been but a few years dry before the first “incident” took place between the powerful city-states. It was right in the midst of that botched mission, at the moment of execution, where Swain now found himself at. He could see the platform where the young prince was standing, his back turned, oblivious to his plight. The poison-bolted hexbow felt heavy in Swain’s hands. “I am impressed. I didn’t expect it to be so real.” ...

Serious question.

Source: http://leagueoflegends.wikia.com/wiki/Swain/Background