Fire elemental crossbow

Crossbow devices with a magic targeting system that project a red light on their targets increasing their range.

Were first seen wielded by the Goblin sentries guarding Qaratta but then later on in the hands of the Clan Veshtak Kobolds when they were harrassing Riverglade

We are assuming these were created by The Builders

These may have been what the Myconids were referring to when they said that the Goblins "throw fire".