Evil evil? Like have the players pissed at you for years evil?
Try this. Normal throne room with lots of cool treasure and coin. Most magic being slightly lower level than the players would expect. Liberal use of false auras to make the place look better than it is.
At the base of the throne, have a small secret compartment that only the Thief in the party notices {pretty good chance of that happening without pushing for it}
In the trapped secret compartment {poison needle, dangerous but likely to be avoided} is a small, plain box.
In the small plain box is a slip of paper and a ring.
The slip of paper says something like:
With this ring, the greatest power will be yours. Wear it and speak Forseti's Oath and your greatest wish will come true
{Forseti is from the Norse pantheon, ("The Presiding One") Axe-God of justice, savior of the devout, winner of just lawsuits. He represents justice, good laws, arbitration, peace, fairness, good judgment. Son of Balder and Nanna.}
The ring is, of course, Mordenkainen's Magical Disjunction with enough power to destroy all the magical treasure in the room and the force fields that are holding the weak pillars from collapsing in on the throne room....
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alternatively, if you like moral challenges and are not squeemish,
the guards to the throne room are all kids. Well, the majority of them are starved prisoners who will run to the heroes as their saviors. 1 in 5 or 1 in 10 are a form of undead who have vampiric touch, which their fellow children have been made immune to. These ones rush forward gleefully for a completely different reason.
Describe the attacks as raking claws as the touch of the guardians opens the skin of their target like a cutting torch.. and the PC is unable to determine which of the younglings the touch came from.
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If your group can handle inter-party conflict,
Have a trap that teleports them to a special chamber that is surrounded by mirrors and has a masking illusion that makes the other PCs appear to have been turned into some sort of undead creature. One mirror per adventurer reflects the image of them surrounded by similar undead creatures, but at a distance.
The end result is the PCs all thinking they have been split apart and facing their own personal demons.
To keep the illusion going better, you have to describe the attacks on the 'demons' and then when the 'demons' attack back, have them deal the damage to the PCs. That way the players don't get alerted to the trick early by having Fred's damage applies to George.
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The throne is a conduit for the Demi-liches of past leaders of the cabal. When a successor could, they would destroy the current leader and channel their essence into the Throne, and then with the leaders Stave they can control that power and memories/spells as they sit upon the throne channeling this power as if it was their own.
Of course, since it is evil, the Throne taints any character that sits on it as the banished Leaders are trying to get their way back. Possibly attempting to possess any weak being {PC} that sits upon the throne.
Of course, destroy the throne and you destroy the magic entrapping the demi-liches in it.. releasing them with their full power and anger.
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The throne is an artifact from an ancient age, from a civilization that was wiped out from a magical disease. The Throne still holds this disease and any who touch it get infected. The Cabal knows about this and have developed a protection against it for the inner circle. They use this as a way to keep un-wanted visitors from the throne room.
Once the PCs 'win' by destroying the Cabal, they carry the disease out into the world were it might yet again take down a civilization.
This leads to an adventure/quest to dig back into the Cabal's library to find the cure..
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Eberron setting:
The Throne is one of the Gateway seals to Xoriat, which the Cabal has been using carefully to siphon the power of the plane of madness. Destroying it opens the portal to Xoriat
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I hope you have a wonderful game!
