ooc: let's assume that the glass is still on top of the gem and Graven has his hand on top of the cover.
The red light that started to emit from the gems grows brighter and after a few seconds it emits three blinding red pulses. Then the glow reduces to a soft warm glow. The room, however has changed somewhat after those three flashes. The door seems to be gone. The wall seems uninterrupted where the door once was. Lord Graven also seems to be missing. What is new, is that there are numerous chains hanging from the ceiling, slowly rocking as if some breeze is stirring them (although you don't feel any movement of the air).
In the back of the room you see a vague shape moving, accompanied by the sound of clattering chains.
[sblock=knowledge the planes DC 13]
This can be nothing other than a Chain Devil, also called a Kyton.
Normal weapons have limited effect on these devils. It is said that a blessed or silver weapon has more effect in harming them.
They are also immime to any harmfull effects based on cold.
[sblock=knowledge the planes DC 18]
These creatures are masters of thier chains, able to control and animate any chain and cause them to sprout barbed hooks.
They shrug off the magics of weaker spellcasters without any harm done and
are capable of regenarting lost limbs.
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[sblock=Knoelwdge the planes DC 23]
A chain devil can make its face resemble one of an opponent’s departed loved ones or bitter enemies, causing one to attack without resolve or hold back on his attacks.
A chain devil’s natural weapons, as well as any weapons it wields, are treated as evil-aligned and lawful-aligned for the purpose of overcoming damage reduction.
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You guys go now! The room seems 30 by 30 feet and the ceiling 15 feet high. The vague shape is in the far right corner.