The Cave of the Majick Chair

This first appeared over at  K&KA in this thread  i've edited this version slightly

Deep in some forgotten cave is the Majick Chair. If you can climb down the rushing waterfall without being impaled on the stalagmites below you can climb the steps to the shelf of rock where the Majick Chair waits for someone to rest their laurels upon it.

The effects of the chair are as follows if the chair 

If someone sits in the chair, roll a d6;
1. A bunch of spiders come out (GM to determine HD and #Appearing)
2. The subject is ejected from the chair (save vs Stalagmite _2)
3. A monster appears and attacks (GM to determine).
4. Subjects is transformed into a stalagmite or stalagtite 

5. The stairs turn into mud (Save vs Stalagmite +3)
6. The Majick Door opens. 

Notes regarding the properties of The Chair and its Environs

The chair only works when there is one person in the room. 

The door is locked and  cannot be lock picked or broken and is 100% magic resistant. What's beyond it and the location of its key are up to the referee. 

If the PC's figure out that the stalagmites and stalagtites are victims of the chair, they can attempt to dispel the effects one at a time. 

The magic of the chair is too powerful for more than one to be freed at a time. 

The stairs turning to mud won't be evident until they are tread upon. They will return to normal in 12 hours.

The chair will only function once every 24 hours. 

Stalagmites do 3d6 piercing damage if anyone falls on them (Save for 1/2 damage). 

The personalities imprisoned in the cave are up to the GM as are the random monsters.