Situation: Party has trapped the soul of the unique pit fiend Liebdaga from The Infernal Syndrome of the Council of Thieves adventure path. What now?
Background: Party picked up two 10,000 gp rubies from the temple of Orcus in the excellent Tomb of Abysthor module. Rather innocently, I mentioned that one of the books in the high priest's room detailed a ritual for trapping a outsider's soul within a gem. Sorceress and rogue, two person campaign, both got excited and haven't let go of the gems or book.
After meandering from one situation to another, our players rescued a hellknight and brought her back to cheliax, thus segueing into the Infernal Syndrome. While in the dungeon, party allied with the succubus cleric. Succubus dominated the medusa sorceress that was encountered near the end.
Now, enter our big bad. The weakened, but still minor hell noble Liebdaga the pit fiend. Party breaks the cage while Succubus, who had the amulet of the twin, waits anxiously. Cage is destroyed and in the round the party has to act before Liebdaga is free, medusa uses her gaze attack, and the pit fiend fails his save. Hmm, well that was anti-climatic.
Party, including the succubus and her medusa play toy, decide dismember the statue then undo the effect. Sorceress readies the ritual, pit fiend is restored to himself only to find his limbs missing and a succubus being very friendly with him. Death ensues and the ritual captures the soul.
Now, the ritual in the books gives various suggestions for using a captured soul: using it as spell focus to modify the effects, intelligent item starting points, etc. So, my question for you all is what should this thing do? What happens when you cast a soul through a noble pit fiend?
P.S. Party now also has celestial with the broken soul template. Same as above, what's it do?