Monkey skull

The monkey skull can be seen in an inaccessible room packed with Monkey Zombies in the Temple of Marimbo Dungeon under the Temple of Marimbo on Ape Atoll. It used to be impossible to obtain because the 'locked door' to the room is (according to the minimap) a wall. This also means that it is impossible to cast Telekinetic Grab here.

On 22 February 2010, the update to Impetuous Impulses made the monkey skull an obtainable item. The skull, although untradeable, can be looted from zombie implings and can be made into a new type of monkey greegree. This greegree allows the player to transform into an ape similar to the bearded gorilla greegree. This new ape has a blue face.

It should also be noted the odds of gaining a monkey skull from a zombie impling jar is very rare.