Inspired by Nufrut.
This assumes an Infernal is CR 43 (Pd scale). Ritual adds +18 in free factors - I've assumed that in compound spells that a spell which is an eligible ritual contribution for either seed is eligible for the final spell. This spell stretches the limits of mitigation a little. Costed on the basis of SP, rather than USP - which might be a little cheap.
Or not. XP and component cost is sizeable.
Infernal Oracle
Conjuration (Calling)[Evil, Lawful, Mind-Affecting]
Spellcraft: 38 ranks
Components: V,S,P,XP
Casting Time: 1 day
Range: 75 ft.
Effect: One conjured infernal, confined to a glass jar
Duration: Permanent (D); see text
Saving Throw: Will negates
Spell Resistance: Yes
Development
38 days; 38,000 gp; 1520 XP
Seeds: [Call], [Binding] (S)
Factors: Increase target CR (+52), metamorphosis (+8)
Mitigating Factors: Free factors (-18), power component (-10), burn 2500 XP (-10), extend casting time (-10), restricted (-10)
Feats: Animus Invictus
Description
From the steaming fringe of Hell, you call an LE infernal whose name is known to you, and confine its essence in a specially prepared receptacle: a crystal sphere approximately 1 foot in diameter. If the spell is successful, the fiend's head appears within the sphere. It may speak, but cannot use any of its special powers or spell-like abilities. The infernal's native immunity and any nonepic spells which provide protection against [mind-affecting] effects are ineffective against this spell.
Typically, the abomination is irascible and unhappy with its confinement, and you exercise no special control over its attitude to you: the infernal may reluctantly concede to a period of enforced servitude, however, if assurances are made to release it at an agreed future date, or it might resentfully aid you if threats (such as abandoning the sphere in a celestial ocean) are made against it. The infernal will lie, maneuver and dissemble to the best of its ability, but is powerless to prevent the use of spells which reveal falsehood, or spells which subsequently force servitude and compliance from it (such as dominate monster), although it is entitled to a saving throw as normal to avoid such effects.
If it comes into contact with weak-willed or gullible characters, the infernal will attempt to convince them to release it (Diplomacy +52, Sense Motive +51) by smashing the sphere: the owner of an infernal oracle may wish to take steps to prevent this by use of hardening or an epic spell using the fortify seed. The sphere is treated as an ongoing spell effect with regard to attempts made to dispel it, and a disintegrate spell or spell using the [destroy] seed destroys the sphere but releases the fiend unharmed.
An infernal oracle possesses formidable knowledge skills, which may prove useful to its owner, provided that the fiend's veracity can be monitored; as a powerful fiend, it may possess special specific knowledge of the Infernal regions and diabolic affairs.
Power Components: A flawless crystal sphere (worth 10,000 gp), powdered opals (worth at least 40,000 gp) and a carved statuette of the infernal to be captured (worth 50,000 gp).
XP Cost: 2500 XP.
Ritual Spell: An infernal oracle spell requires the participation of six additional spellcasters, each of whom contributes a dominate monster spell.