I actually have developed two spells exactly for this type of use. The first prepares the skull (my character is a halfling shaman so carrying around a large skull is too much. shrinks them down like a head hunter would). The second spell is the retriever/reader spell.
Spell: Seebora's Totem Skull
Level: 3
Components: V,S,M
Casting Time: 1 Hour
Range: Touch
Saving Throw: None
Duration: Permanent
Description:
This spell shrinks and cleans a skull down to 1/12 its normal size. By placing a skull from a non-living being, which has never been previously animated, in a water/herb solution and casting this spell, the skull will lose any and all fleshy parts (down to the bone) and shrink to 1/12 its normal size. The skull will "harden" in that it it will gain a AC 12, hardness 8 with 20 hit points.
The process is like a super dehydration, and does not make the item magical, but the effect is permanent, and cannot be dispelled.
The skull once created into a totem will be just as if it had never been shrunk, but will he smaller and harder to destroy. Any spells that would work on a normal skull will work normally on a Totem Skull.
Material Components: One skull from a corpse that has never been animated by a animate dead type spell. Herbs and roots worth 10gp per size category of the base creature mixed in a water solution large enough to submerse the skull.
Spell: Seebora's Mind Search
Level: 7
Components: V,S,M
Casting Time: 8 Hours
Range: Touch
Saving Throw: WILL(Special)
Spell Resistance: None
Duration: Permanent
Description:
This spell allows the caster to probe a prepared skull and retrieve prior knowledge that it had.
This is an improved version of Speak with Dead. It allows the caster to concentrate and search/question the skull for information that it had known when it was alive.
Since the skull/being is dead, it does not get any Spell Resistance, but it does get a one time WILL save to resist the spell, though at a -4. If the skull makes it's save, then the spell fails and the skull cannot be the target of either Speak with Dead or Mind Search again. It also cannot be animated. If the skull fails the save, then it is properly prepared for future use.
Also the skull could not have been the target of either a Speak with Dead or Mind Search prior to casting of the spell, also the corpse from which the skull was taken could not have been animated prior to casting. This includes low level undead, but higher undead and natural undead (those that came alive by curses or unnatural means) can be included. Excluded Skeletons and animated constructs/beings. Included, vampires, wights, lichs, etc.
Once the spell is cast on the skull, the skull is prepared to be searched at any time in the future. Any information that the being knew during its life can be searched. Though a concentration check is required to retrieve any information. Even though the skull has been prepared and "indexed" it still takes time to concentrate and retrieve the information. The more personal/private the information, the longer and harder the concentration check is required.
The base concentration check has a DC of 10, Common/public knowledge has a +5 DC, Uncommon Knowledge has a +10 DC, Private Knowledge has a +20 DC, Secret Knowledge has a +30 DC. Forgotten or Knowledge Magically sealed/locked also adds a +30 DC.
Also the amount of detail trying to be researched is factored in. General information is +0, while moderate details are +10 and specific details are +30. For example, searching for information about a meeting, his body guard was there, is general information, his name was "gerard" in moderate details while the spelling would be specific details.
Also the futher back in the history of the skull/being the harder it is to search as well. Add a +1 to the DC for every 10 years back. This applies in the beings life, not the life of the skull/corpse.
The time required to search the information is based on the DC check. For every point above 10 takes 1 minute. So a search on common knowledge would take 5 minutes.
The information retrieved is as the being knew it when they were alive. It is not encrypted or misleading, unless the being who knew the information was mislead.
The caster can search as much and as often as they like given the time.
DC Modifiers (Base of 10) [add all that apply]:
> Personal [First hand] Information +0
> Non-Personal (Second hand) +10 [someone told me rather than being there]
> General Detail +0
> Moderate Detail +10
> Specific Details +30(minimum)
> Common Knowledge +5
> Uncommon Knowledge +10
> Private Knowledge +20
> Secret Knowledge +30(minimum)
> Magically/Psionically Blocked +30(minimum)