The Temple Investigation 2
Start and complete it with Locked Door in Inside the Temple 2.
Requirements
Lv. 18+
Quests
Objectives
Defeat
Collect
NPCs
Locations
Locked Door Start, Complete
Connected quests
Dialogue
Turning in the quest
Additional replies
(The Sewer Rat have keys that seem like they might open the lock. Eliminate 50 of them and obtain 
Silver Key x25.)