Making a special Staff

[MaxMAnAtArms]

Im working on finishing a staff for a game I am in. Its going to be a magical staff that helps boost my magic (naturally) Which is conjuration/Necromancy and evil. What I have planned is it to look like two hands upside down holding the staff upright bones forming the length of it and middle is wrapped with undead "wrappings" i.e Mummy wrappings and Undead flesh (zombie/vamp/wight/etc) And the top have a hand with 2 thumbs one on each side.

What I want is the top hand to be able to hold a Darkskull. So when I "set up" the staff the hand closes around holding the skull in its grasp and the ability to remove and store it away when i don't want a 40ft unhallowed area around me.

I know allot is going to be DM okaying and such. But is there any in game mechanic that would work to such a degree?
I want to have some "this is in the game I'm just tweaking it in a valid possible way" so its not like I'm going "it sticks magically"

I was thinking maybe rigging it up slightly like a Rod of surprise where i use a bottom to control the closing process. Would this make sense logically

If I make it out of metal would that work better if I use a "trinket" magic item to animate object to make it "walk" and grip things?

or is it to far out there?

[Uncle Pine]

Darkskulls are slotless items. If you're crafting a custom staff, you can just carve a hole slightly smaller than an item in it and stuck it inside. A particularly demanding DM might require you to apply sovereign glue to make it sure it doesn't "accidentally" fall off at the very worst moment, or whenever you happen to walk near a deep chasm.

Regarding turning the darkskull on and off at will, just drop a piece of cloth on it when you don't need the unhallow effect. Line of effect rules (http://www.d20srd.org/srd/magicOverview/spellDescriptions.htm#lineofEffect) state that solid barriers block emanation spells. A(n oversized) candle snuffer could also work.

[Falontani]

If you take the feat: Item Familiar then your staff will have Sentience and can activate and move parts connected to it by itself. If you have a skeletal hand at the top then it would be able to grip just like a skeleton could anything place on top of it. Otherwise you could enchant it as a sentient item (CL 17+)
Bind a fiend of possession and have it possess your staff.

[Acanous]

Animate object could also work.