The witchdoctor legs are a reward from the Herblore Habitat. To receive this item, the player must succeed in catching all ten normal jadinkos in the same week (you will receive a message from Papa Mambo). By talking to Papa Mambo, you will have a chance of receiving this item.
From the moment you first wear this item, you receive a 1% boost on Hunter, Herblore, and Farming experience for 30 minutes. The boost percentage stacks with the witchdoctor mask (2%), and witchdoctor robes (2%). This experience boost can be renewed each week by catching every god jadinko, and the bonus experience lasts for 1 hour from the time you talk to Papa Mambo.