A very long time ago, when the party was first level, they frequently came up against Spider Monks, a surviving fragment of an ancient cult of geometers who'd made ties with spider-based powers (particularly Rakni, as they later discovered). One of the weapons in the Spider Monk arsenal was an orange gas that destroyed any organic or magical matter that came in contact with it...or so the party believed for many years. In fact, creatures trapped in the orange gas are transported to the Dustplane, a demi-plane in the Astral somewhere between the Prime and Acheron; their magic items are transported as well, though they may go to another destination. Most people aren't prepared to suddenly find themselves without most of their equipment, and once they arrive on Dustworld, they probably don't last very long. (The "dice" used by the Spider Monks were not of Rakni's making; Hajmola may have had a hand in them, as a way of ensuring that Rakni and her orange gas became everyone's problem. Detailed notes about the dice can be found on Ganeth's character sheet.)
Dustworld was designed and largely created by mortal Geometers once upon a time, and monks may have used it for high-level training. Unfortunately, Rakni seems to have found a way to block the exits from the plane, trapping any souls and spirits who go there and using their energy to power her own ambitions. This has tended to make missions to Dustworld extremely unattractive; adventurers have a habit of risking death, but having their souls and spirits trapped forever, preventing raises, reincarnates, or anything else from bringing them back, is a bit much for most folks. (This development probably also explains why there have been no monks of 7th level or higher for a very long time.)
It may be that several years ago, the original Partners in Crime, Plant Dude and Hajmola, placed some bets on the party destroying the Dustplane. Since then, Ganeth has become the Red One, and both Hajmola and PD have been spreading the word that G is going to take Rakni out. Rakni hasn't exactly taken this advertised Red One vs Rakni matchup well, especially since the party has been somewhat active in opposing her operations on the Prime, and she's tried on several occasions to use the infamous orange gas to send the party to the Dustplane...which is just what the Partners in Crime may want, though she doesn't know it. Meanwhile, several other evil factions, particularly those associated with the Alliance for Law (which Rakni broke away from not long before the shadowing), are more than happy to pit the party against Rakni, since they come out ahead either way -- especially now that the party has become involved in the Western War.
It seemed clear that sooner or later, the party would be going to the Dustplane; either Rakni would succeed in dumping the gas on them, or they'd come up with a plan for destroying the plane and go themselves.
In the end, neither came to pass. A consortium of devils, many associated with the Alliance for Law, contracted with another lower planar being (a follower of a geometry-based religion that seeks to understand the Ideal through study of the dodecahedron, which they argue is the most spherelike of the Platonic solids) to kidnap Ganeth and ship him off to Dustworld. To ransom him back, most of the party has agreed to go as well; if you're probably going to Dustworld anyway, at least go when you have time to prepare. (While a rescue mission was briefly considered, it was scratched when Silvana realized the booby-trap on the demiplane where G was being held was probably a pile of orange gas that would send them all to the Dustplane anyway.)
The Seed Crystal is an octahedron, and the Lesser Crystals are cubes; each Lesser Crystal is linked to a face of the Seed. The crystals may be diamonds; the liason said that they were clear with a high refractive index. Aside from the timed regenerations, a skilled user can use the Seed Crystal to start a refresh at any time.
The Consortium has operatives on Dustworld trying to learn more detailed timing information, so the party may have these details when they arrive. But since arrival locations are unpredictable (though deterministic), the party may not be able to meet up with these people (if they're even still alive).
According to Ganeth's captor, the crystals are meditation aids; when used properly (as monks are trained to do), they can grant powers to their users. When used improperly, both the crystal and the user may be damaged, and this could be a method of disrupting the information stored in a crystal. The crystals are also thought to be moveable (though not by physical strength), so it may also be possible to use crystals to physically damage each other. (Note that crystals that are moved are likely to return to their starting location during a refresh.) The liason told Ganeth that he would likely need to rely on "dodecahedron technology" while on the Dustplane (which is called "Halfway to Paradise" in the liason's circles); its only advice on doing this was, "It must be pure. All else follows from this."
To make life a little more exciting, the Dustplane is likely to drive much of the party insane during their stay: The elves will slowly descend into catatonia if away from trees for too long, and the Chaotic members of the party will suffer additional insanity-related problems if they come under stress. Since Beeel, as a Lawful human kensai, will possess the greatest resistance to the plane's effects, the party has chosen him to lead the mission. (But whether anyone else will be sane enough to follow his advice is an open question.)
In the best of all possible worlds, the party will be able to free the exits from Dustplane and escape the plane before it's destroyed. But given the odds against this happening, certain contingency plans have been made. Beeel has accepted sponsorship from the ki-rin, and Frankel is now sponsored by animal-related beings from the Beastlands, so if their souls/spirits manage to leave the Dustplane, they'll be back. The grey elves and Pepper will, as usual, be returning via Plant Dude and the Grey Elven Forest. Thorongil has commissioned a clone of himself from Argon; if his spirit is recovered, it will be placed into the cloned body, otherwise Argon will fully grow the clone and release it, so in any case, the world will have a Thorongil.
Ganeth's case is somewhat more complicated, as the devils are going to be handling his return. If their (rather sketchy) plan works out, Ganeth's body will be intact at the end of the mission, but his mind will be shattered by the Red One's backlash, so the devils intend to revive the body and rebuild the mind, adding "filler material" where needed. (The party has also contracted to have a point of constitution added to the body, at a cost of 3000gp.) If the body is destroyed, however, the devils have contracted to have a new one grown, which will cost them a bundle but allows improvements to be made more cheaply (a point of constitution and a point of intelligence -- pricey, since high stats are harder to raise than low ones -- for about 4500gp; after items and other effects of dying, the net effect would be to preserve G's intelligence, avoid a con penalty when the body hits middle age, and eliminate the wisdom penalty on saving throws). Another plus to the regrown body is resistance to the anti-plant magics that are the bane of elves; drawbacks are sterility (not a problem for someone who's probably too paranoid to remove his armor long enough to have sex), possible incompatibility with Plant Dude, and token damage from holy water and other material-based (rather than alignment-based, since G will remain CG) holy hosers. So G's goal is to keep his mind intact and not worry so much about his body, while the Consortium's goal is the opposite; unfortunately, the devils have implanted a few instructions in Ganeth to help insure the mission concludes as they desire. (No other behavioral modifications have been made, however, since they would add to the strain of staying sane; they can do all that with the filler material later on. Ganeth, as a low-wisdom Chaotic, will be at least slightly insane for his entire time on Dustworld, but if he goes completely around the bend and detonates prematurely, nobody wins.)
In a bid to counter the devils' future modifications, Ganeth has asked Beeel to make sure that after his return, he gets checked out by the Holleriths, the Cuthbert, the ki-rin, and/or whatever other powerful Good types are willing to figure out what was done to him and fix it -- chances are he'll be programmed to be less than cooperative after he's back.
Since magic items won't make the trip to the Dustplane, and any other equipment the party brings won't return, most of the party will be leaving its items with the Moradin-worshipping dwarves in the mountains. The Consortium will retain custody of Ganeth's items until his return (and will probably do something subtle but nasty to Elissa, his intelligent longsword, while they have her). After de-iteming, the party will enter the Veins of Abbathor, which contains the Consortium's departure point to the Dustplane. Meanwhile, Ganeth will be sent down directly from the altar, after being healed and having a chance to memorize spells; Silvana has arranged for a team of medium warhorses to make the trip as well. Fully organic weapons and a guide have been provided (for a fee) by the Consortium; unfortunately, bone weapons are a damage class below normal metallic or stone ones.
If the party fails in their mission, the effective result will be a timejump; at some point in the future, somebody probably will manage to destroy the plane, and all of the recovery pacts will go into effect. (In the meantime, Silvana speculates that they might reincarnate through several lifetimes on the Dustplane, becoming ever more insane as they go.) If they succeed, things are likely to heat up on the Prime as Rakni, no longer able to bide her time and soak up energy from the Dustplane, puts her plans into high gear and explodes across the continent. Her tit-for-tat policy may translate into an attempt to destroy the Grey Elven Forest (a demiplane that sponsored the destruction of hers); the Partners in Crime have a plan to prevent this, but Hajmola may escape Plant Dude's clutches in the process. Apart from Hajmola's tendency to complicate the party's lives (though of the three would-be gods, he's far preferable to Rakni or the Shade Lord), this would also cause the Alliance for Law to become more active on the Prime as they attempt to capture Haj themselves. And the liason admitted that the Eightfold Path, where Streck disappeared to before the Shadowing, is the dual of the Dustplane, so the megalomanic high elf may be returning after this mission as well...to discover that the clan he left in Ganeth's care is all but gone and (perhaps) that Kharnzeel has taken up residence in the Nirduk Vault.
Hang on, folks...this is going to be nasty.