Zombie head
Grinning obsidian idol was removed from RuneScape after an update, but still exists in-game for those who had obtained it.
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Grinning obsidian idol detail

The grinning obsidian idol was a Squeal of Fortune promotion. Grinning idol parts appeared on the Squeal of Fortune on 18 October 2013 and were available there until 28 October 2013. All parts were removed on 8 November 2013.

Four parts (three parts for free players) compose the idols: bodies, legs, and arms for free players, plus heads for members. Parts could be used individually for experience or combined for more experience.

Parts could be traded with other players on a like-for-like basis. So any head could be traded for any other head, bodies could be swapped for other bodies and arms or legs could be exchanged for either arms or legs.

Note: Combat experience could be toggled off by right-clicking the idol and toggling Combat experience off. The removed experience was NOT distributed among the other skills.

To combine pieces, players started with a body, then attached the legs, arms, and head of the same material in any order. Once activated the idol was consumed and awarded bonus experience in the following skills: Attack, Dungeoneering, Farming, Fishing, Thieving.