Very nice thread. This is the main reason why im still playing this game. Been on and off since 2004. I love the mysteries, and unsolvable quests and unreachable areas.
Like Nostrax said, the teleporter in dara d lair IS the music box quest:) Also the part of the desert quest in jakundaf desert involving the hall of lost doors. is infact a quest aswell, it will give you some sort of a flute if im not mistaking, Did it a few weeks ago. Many rooms and doors to unlock with different ancient forgotten keys. http://tibia.wikia.com/wiki/Hall_of_Lost_Doors .Thou even after weeks of searching, me and my friend couldnt find a way in to the banshee and the teleporter. Maybe theres still some more hidden deep in that cave. You should read the theory about lowering the water in Jakundaf desert, to access te corpse on the island with the palm tree. And also we did manage to find some info about the beholder language in books deep down in the cave.