I couldn't open the door that ''sealed by drow sorcery''.How can i open it. Please write

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if it's in the underdark, the Koa-toa dungeon, you need Adalon's aid in opening the door.

Who is this Adalon you are talking about and where can i find him?

HER. Have you encountered the svirfneblin yet?

I rescued the boy from crystal and i killed a demon for them.Now i have a stone but i can't talk with svirfneblins they just trade.Where is thwt Adalon?

Go talk to the svirfneblin who told you to go kill the demon.

(Are you ready to do some ROLEPLAYING? You'd better be! :D )

i'm not absolutely sure what part you're talking about, but i think i know...
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spoiler!!!
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first, you need to talk to the svirfneblin after killing the demon and he'll give you the light gem or something like that. then you can go in the cave that used to say "you need light to enter here" (these aren't exact quotes cause i didn't memorize what they said). you will speak to Adalon who is a dragon. after talking to her (be nice and agree to help her out) she will make you and your party look like Drow. then you can enter the drow city which is a huge part of the game.

oops forgot to tell you something...
SPOILER
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there are 2 or 3 svirfneblin you should be talking to after you kill the demon, (from the demon pit) they are down as far as you can go, and to the left. one runs a store, and the other is in a place with lots of beds. (make sure you filled up the pit the demon came from witht the earthquake spell that the svirfneblin gave you earlier.