- Talk to Burga
- Go to the rival compound
- Kill 11 spiders
- Collect spider stingers
- Return to Burga
- Collect the rat.
Ah.. Progress! Burga the Shaman is willing to make a deal. For a price, of course. He hates the neighboring Orcs because they worship a spider god and he's more of a rodent traditionalist. He needs you to go over to their compound and destroy their supply of spiders. He wants you to collect their stingers as proof. So much for trust.
Go to the compound to the north, kill all spiders and their handlers and return to Burga with the proof. He'll give you a nice fat rat to take back to Fellir in Karagh.
On some occasions, I've had one spider NOT drop a stinger, or one too few spiders get spawned. The solution is to save the game, exit and reload. The stinger or the remaining spider will appear.