I turned my thoughts to the question of binding Graz'zt, and came up with the following suite of spells. They are all optimized around the idea of a coven of 6 high level wizards (as Fillein's version is). Toughness of Body is to help soak up backlash damage, while Sharpness of Wit is to make subsequent spells almost impossible to save against. The Sphere of Irresistable Magic and Mist of Dreams are centred on the thaumaturgic diagram where Graz'zt is to be called. Unless Graz'zt has buffed himself quite extensively, he will find his SR sharply reduced, and thus will be unable to resist the Mist of Dreams. The latter spell should render Graz'zt utterly catatonic (and therefore helpless). If it does not, he might actually be able to escape.
Rather than keying the ward seed to overcome mind-blank, it overcomes all magical protections of up to 10th level (i.e. epic spells and below). I figure that in the time since Graz'zt's first binding he may have developed magical countermeasures against being called unwillingly. Such (hypothetical) protections are ineffective against this version of Call Graz'zt.
Call Graz'zt has a brief duration, so his captors will wish to act quickly to finally dispose of him. Binding or Trap the Soul are both possibilities. Or a character with a Wisdom of at least 33 could enter the Mist of Dreams and chop off his head (coup de grace).
The full sequence requires 6 each of 5th, 7th, 8th and 9th level spells, and 5 epic spells. One 21st level epic spellcaster could cast all the spells over the period of three days; Toughness of Body and Sharpness of Wit can be cast on 6 pm of day 1, the circle can be prepared with Mist of Dreams and Sphere of Irresistable Magic at 1 pm of day 2, and Toughness of Body and Call Graz'zt can be cast at 8am of day 3.
Three epic casters working in parallel could research the spells in only 4 days, for a cost of "only" 468 000 gp.
Toughness of Body
Transmutation
Spellcraft DC: 11
Components: V, S, Ritual
Casting Time: 1 round
Range: 0 ft.
Area: 20-ft radius sphere centred on you
Duration: 20 hours
To Develop: 99,000 gp; 2 days; 3960 XP. Seed: fortify (DC17). Factors: grant additional +39 enhancement bonus to ability score (+78 DC), 1-round casting time (+18 DC), change from touch to target (+4 DC), change from target to area (+10 DC). Mitigating factors: 6 secondary casters contribute 7th level slots (-78 DC).
All characters within a 20-ft radius circle centred upon the caster gain a +40 enhancement bonus to Constitution, with the appropriate changes to hit points and Fortitude savings.
Sharpness of Wit
Transmutation
Spellcraft DC: 11
Components: V, S, Ritual
Casting Time: 1 round
Range: 0 ft.
Area: 20-ft radius sphere centred on you
Duration: 60 hours
To Develop: 99,000 gp; 2 days; 3960 XP. Seed: fortify (DC17). Factors: grant additional +63 enhancement bonus to ability score (+126 DC), 1-round casting time (+18 DC), change from touch to target (+4 DC), change from target to area (+10 DC); +200% duration (+4 DC). Mitigating factors: primary caster sustains 42d6 backlash (-42 DC), six secondary casters each sustain 21d6 backlash (-126 DC).
All characters within a 20-ft radius circle centred upon the caster gain a +64 enhancement bonus to Intelligence. Wizards thus enjoy a bonus of +32 to the DC of their spells.
Sphere of Irresistable Magic
Enchantment (Compulsion)
Spellcraft DC: 10
Components: V, S, Ritual
Casting Time: 1 round
Range: 300 ft.
Area: 20-ft radius sphere
Duration: 20 hours
Saving Throw: Yes (see text)
Spell Resistance: Yes (see text)
To Develop: 90,000 gp; 2 days; 3600 XP. Seed: afflict (DC 14); ward (DC 14). Factors: Additional 29 point penalty (+116 DC), +32 to caster level checks to overcome Spell Resistance (+64 DC), 1-round casting time (+18 DC), change from target to area (+10 DC), effective vs mind blank (+14 DC). Mitigating factors: primary caster sustains 30d6 backlash (-30 DC), six secondary casters each sustain 15d6 backlash (-90 DC), six secondary casters contribute 8th level spell slots (-120 DC).
Creatures within the Sphere of Irresistable Magic suffer a -30 penalty to their SR for as long as they remain there. The creature's spell resistance must be overcome (check only once), with the caster gaining a +32 to the caster level check. A will save also applies (DC 20 + caster's ability modifier), but each round that they remain within the Sphere of Irresistable Magic they must succeed at the saving throw – failure indicates that they suffer the effects until they leave it. Leaving and then re-entering the zone prompts a further saving throw.
Mist of Dreams
Enchantment (Compulsion)
Spellcraft DC: 10
Components: V, S, Ritual
Casting Time: 1 round
Range: 300 ft.
Area: 20-ft radius sphere
Duration: 20 hours
Saving Throw: Yes (see text)
Spell Resistance: Yes (see text)
To Develop: 90,000 gp; 2 days; 3600 XP. Seed: afflict (DC 14); ward (DC 14). Factors: Additional 31 point penalty (+124 DC), 1-round casting time (+18 DC), change from target to area (+10 DC), effective vs mind blank (+14 DC). Mitigating factors: primary caster sustains 30d6 backlash (-30 DC), six secondary casters each sustain 15d6 backlash (-90 DC), six secondary casters contribute 5th level spell slots (-54 DC).
The forces of the unconscious are released to overwhelm affected creatures with powerful waking dreams. If a creature's SR is overcome and their will save failed (DC 20+ caster's ability modifier), they suffer a -32 penalty to their Wisdom scores for as long as they remain within the affected area. Each round that they remain within the Mist of Dreams they must succeed at the saving throw – failure indicates that they suffer the effects until they leave it. Leaving and then re-entering the zone prompts a further saving throw.
Call Graz’zt
Conjuration (Summoning)
Spellcraft DC: 10
Components: V, S, M, Ritual, XP
Casting Time: 1 round
Range: 75 ft.
Effect: One summoned demon prince
Duration: 20 rounds (and see below)
Saving Throw: Will negates
Spell Resistance: Yes
To Develop: 90,000 gp; 2 days; 3600 XP. Seeds: Compel (DC 19), Summon (DC 14); Ward (DC 14). Factors: gain +16 bonus on caster level to defeat SR (+32 DC), ward effective against all magic (+180 DC), summon specific individual (+60 DC), full round action to cast (+18). Mitigating factors: primary caster sustains 42d6 backlash (-42 DC), six secondary casters each sustain 21d6 backlash (-126 DC), 6 additional participants contributing 9th level slots (-102 DC), each caster burns 800 XP (-56 DC), 5000 gp cost (ad hoc -1 DC).
In a brief ritual requiring six additional participants, the spellcaster conjures and confines the demon prince Graz’zt into a readied thaumaturgic diagram. This diagram takes a day to draw, requires a DC 40 spellcraft check to complete successfully (the caster may take 10), and requires 5000 gp in special materials (powdered diamonds).
Graz'zt is entitled to a Will saving throw (DC 20+ relevant ability modifier) in order to resist being called. He can make two attempts to escape from the diagram (and break the spell) by first making a successful Charisma check (DC 30 + 1/2 caster level + caster's charisma modifier), and then by pitting his spell resistance against the caster's caster level check. Note that the caster receives a +16 bonus to his caster level when making this check. Graz’zt’s continual mind blank ability and other magical protections are ineffective against this spell.
Once Graz’zt is successfully confined he may not leave the diagram without aid, nor may he use any of his spells, or supernatural or spell-like abilities. He will remain quiescent, but may still communicate normally with those outside of the diagram. Any attack upon him constitutes a negation of the original compulsion, and he will be free to attack or flee if he survives it. If the circle is broken, the spell is similarly ended.
This spell does not last long enough for Graz'zt to be coerced into service, or for him to make additional attempts to escape. The compulsion binding him to the diagram expires after only 2 minutes. At then point (or earlier, if the spell is broken before then) Graz'zt is free to do as he pleases.