Carrion Farm is an event found in the Fields of Misery in Act I of Diablo III.
When fighting their way through the fields, players may find a large square field which is only open from the NW side. Inside, a Beleaguered Farmer will beg them to aid in cleansing his only source of income from the carrion bats.
To do so, the player must destroy all four Carrion Nests on the patch of the land (do not touch the cow in the western corner). This is not guaranteed to be easy, as those constantly spawn new bats, and even more will pour from the bushes until the nests are taken care of. The last nest will always spawn Sicklefang. After the player defeats Sicklefang, the event can be completed by talking to the farmer.
Potential rewards from this event include Sydyru Bone, which has a chance to drop off the unique bat.