Despana Treasury Key

Despana Treasure Key is needed to open the treasure in the Temple of Lolth in Ust Natha. Phaere will give this to you after you have completed some tasks for her and wants that the player character to replace the Dragon Eggs with Fake Dragon Eggs.

In-game description
"This key. obtained from Phaere, will give you access to the Despana Treasure Room."