A Farm Besieged
From Diablo Wiki
This page provides information on A Farm Besieged bounty.
Trigger: Clicking the "Dead Beast"
On clicking the corpse a couple of packs of Burrowing Leapers will emerge from the ground and attack. After a short while Burrow Bile, a superunique will appear. He has a basic lighting attack but it's his double fisted melee attack that packs a mean punch. Underestimate it at your peril.
After Burrow is dead the farmer will appear. Follow him down to the cellar and there will be a Resplendent Chest waiting for you.
This scenario can appear in Campaign mode but not as an event, with the rewards those bring, it is simply a scenario.