Deranged goblin

Deranged goblin is a deranged goblin, who will be killed during the Cook's Assistant quest. You can talk to Wise Old Man after the quest to hear the story about how the goblin became deranged.

As a young goblin, he used to live in Lumbridge swamp. One day he found a strange mushroom growing under a rock, and since it was blue, he decided to eat it. At that moment Muh-Zhroom, the mushroom god of insanity, claimed the goblin's sanity and stored it in an empty pot. The goblin succumbed to madness, trained 99 Runecraft, and travelled to Dorgesh-Kaan to join a goblin gang.

The fight
He rampages around, clawing with his dirty nails and throwing shit at the player. He's fairly easy to defeat, but you're bound to become diseased, so Relicym's balm and active vaccination are recommended.

Trivia

 * This goblin has never washed his hands.