The origins of this artifact are lost in the mists of time, as is often the case, but tales come to us from the scribes of the ancients as to this object's immense power. The following description might be added to one's own tale of adventure. The text in purple may be read aloud if you like.
... you find the floor of a long hallway is decorated with an undulating bronze bas relief of a great serpent, who winds into a huge chamber 30' by 70', and curves up into an arching sculpture. The serpent statue's wide, flat head shelters a low, simply carved stone throne at the far end of the room. Two rows of mighty bronze shod pillars range down the great hall at 10' intervals, flanking the throne and its sheltering serpent head. The walls appear to be made of much older, heavily pitted stone, which is worked but is so worn it almost appears natural. About 10' behind the arching back of the bronze serpent, a row of mummified scribes sit, their withered hands still clutching stylus and clay tablets.
On a secret door check of a 1-2 on a d6, characters will see that among them sits one who yet lives, as parched and withered as a mummy yet breathing. His piercing blue eyes survey all in the room under heavy lids. If addressed, he will speak in the tongue of the Ancients that he is the last of the scribes of the Room of Change, his sacred task to record the changes that those brave enough to sit in the throne may undergo. He will be glad to inform characters of the changes the throne may make upon them, owning that immortality was the gift that he himself gained from it, but not eternal youth.
If an adventurer sits in the throne, the eyes of the bronze serpent will flare, thunder will peal, and the occupant of the seat will be engulfed in a blinding flash of light. Roll a save vs. wands or undergo the following transformation:
1 Transforms into a writhing mass of snakes, slithering out of clothing and equipment en masse and attacking. There number of snakes is equal to the characters HP total divided by 4. Their clothing and gear can be retrieved from the throne. The character can be returned to normal if all the snakes are gathered alive and a remove curse is cast upon them.
2 Transforms into a serpent ogre, destroying clothing and armor in the process. Roll a save vs. spell to retain original mind and personality, otherwise go mad and attack former allies.
3 Transforms into a mummy, which will rise and attack. Character is dead without chance of resurrection. Gear is retrievable.
4 Strength, Dexterity, and Constitution are instantly and permanently raised to 18.
5 All damage is instantly healed, all limbs restored, and all curses lifted. A dead body seated on the throne may be restored to life if this result comes up.
6 Character is rendered immortal. They cannot die, but continue to age normally. If reduced to 0 hp, rendered immobile until they are healed above 0 once more. All limbs lost will regrow in time, but will reduce the immortal's charisma while they grow back. Even a severed head may be regrown, but the immortal will be blind and senseless while the head grows back.
7 Develops scaly, hairless skin, golden, slitted eyes, and a serpent like tongue. Charisma is reduced by half. Can speak the tongue of serpents.
8 Character's body turns to gold statue. Gear and clothing unaffected. May be cured by stone to flesh spell or remove curse. Weight of body is tripled.
Characters may only sit in the chair once. A dead body placed in the chair will be effected normally, and if the resulting transformation is a living thing(s), they will be effectively resurrected, although perhaps not in a form they might desire.
After the magic happens, the scribe will declare "The Change is Made" in the Ancient tongue, and scribble a note on a clay tablet before him.