The next quest is ready. "Poisoned Water Supply" is another quest from Diablo 1. You can talk to Pepin at the hut southwest of the Wargfels portal in Artamark, near the fisherman.
There is a cave system nearby. On the second level you will find the spring and the source of the corruption. Pitspawn Fouldog has been moved from his former location to be a part of this quest. This new role fits him much better than appearing alone on a dusty road.