Fiendish Codex 2, page 52, magical location (which is in Hell), the Shriver. It's a torture device, and you have to make two saves each round (2 Fort or 2 Will, whichever of your saves is worse). If you make both saves, you gain an ability and can attempt to endure another round to gain another ability. It also deals 2d20 damage to you each round, and the DC 15 save goes up by 1 for every five points of damage you took the previous round.
The abilities gained for staying in each round:
1. cannot be shaken.
2. can’t be frightened or nauseated.
3. can’t be panicked or sickened, and gain a bonus on Fortitude saves.
4. can't become confused or fatigued and gain regeneration 1 overcome by good and chaotic weapons.
5. can't become exhausted and gain a bonus on Will saves.
6. if disabled, you can make either a full-round action each round, or a move action and a standard action, and your regeneration increases to 2.
7. barkskin 1/day as a spell-like ability (caster level 5th) and regeneration increases to 3.
8. regeneration increases to 5.
9. make a concentration check to divert healing spells (within 100 feet) to you instead of the intended recipient.
It only lasts 99 days unless you recharge it by performing evil acts. It is valued at 30,000 gp.