Contract: Missing Brother is a witcher contract in Velen, near the Border Post in the Grayrocks area. On the surface it is not a monster job at all, just a man looking for his missing brother. But Geralt has seen enough of these cases to suspect that a monster is involved somewhere, and coin is coin.
His suspicion is correct. The trail leads to an old mine southwest of the Border Post, and the mine is a nest of arachasae, huge insectoid predators that thrive in dark, damp places. Inside, young arachasae swarm the tunnels, and at the heart of the nest waits a particularly nasty one called Harrisi.
Arachasae are well armoured and some spit venom, so Insectoid oil, Golden Oriole and Igni are all useful here. Geralt finds out what happened to the missing brother, and a Nilfgaardian body in the mine yields the steel sword Gwyhyr. As with many Velen contracts, the ending is grim, but at least the family gets an answer.