The simple way to get into Jaled Dar's lair is to have a rogue with a 210+ skill in lockpicking to open the door. If simplicity isn't your thing, or you just want the key for yourself, you can obtain it one of two ways: Either a quest offered by Zlandicar or a quest offered by Neb.

Once you've found your way into the lair, Jaled Dar's Shade yields the key to Sleeper's Tomb. You'll need to give him either a Talisman from any of the five dragons of the first brood (Zlandicar, Klandicar, Yelinak, Sontalak or Lendiniara).. OR a "Shard of Hsagra's Talisman" which is dropped uncommonly from top giants in Kael Drakkel (King Tormax, Vindi, Statue).

After handing one of these items over, Jaled Dar's Shade will reward you with your key.