A Porcine of Interest

Begin the quest by reading the notice board on the wall behind Fortunato's Wine Shop. A bounty on a "troublesome monster" by Sarah will catch your eye. Begin the quest, and make your way to Sarah in the Falador Farm.

Talk to Sarah, who explains that she was making her monthly delivery to The Sheared Ram when she was attacked by a hulking monster near the crossroads north of Draynor Village, where she lost her cart of farm produce.

Make your way to the crossroads north of Draynor Village and investigate the cart there. Then, follow the trail of farming produce and broken dead trees north-east until you reach a strange hole next to the River Lum. Use your rope on the hole and climb down.

Upon entering the cave, walk to the very end of the cave, where you'll find a skeleton. Inspect the skeleton to find that it has been gnawed clean, alongside a scrawled note:

Suddenly, a Pig Thing attacks you, spitting acid and rendering you unconscious. Luckily, Spria arrives and brings you to her house. NOTE: Chasing a kitten during the cutscene will end the cutscene returning you to the beginning of the cave with no way to recover the lost kitten. Clicking the ground during the cutscene will also return you to the beginning.

Speak to Spria, who tells you that the monster is a sourhog, a creature made through a magical experiment and whose saliva is extremely acidic. She will give you a pair of reinforced goggles to protect you from its acid attack, and tells you that its thick hide gives it a resistance to slashing and magical attacks. She will tell you to kill the sourhog and claim Sarah's bounty, and return to her once you do so.

Return to the Sourhog Cave, and defeat the sourhog. It is level 37, so lower levelled players should bring some food. As stated by Spria, it is weak to stab and ranged-style weapons. To kill it with rings of recoil, one damage must be dealt by the player for kill credit. This particular sourhog is immune to poison.

Upon killing the sourhog, use a knife or slashing weapon to obtain a sourhog foot, which you'll need as proof to collect Sarah's bounty. If you do not have a knife or slashing weapon, you may use the bronze scimitar that spawns near the skeleton at the end of the cave.

Return to Sarah, where she'll reward you with 5,000 coins and tell you a strange woman in a hood came to ask her about the job. The woman she refers to is Spria, whom you were told to return to once you collected your bounty.

Speak to Spria in her house in Draynor Village to finish the quest.

Congratulations, quest complete!