If you are due to get a Promotion Quest for Assault, it will flag, and must be completed before Naja Salaheem will give you this quest. This is no longer true; you will now receive the cutscene for this quest simply by entering the building after flagging Eternal Mercenary. It is no longer necessary to talk to Naja, and so Promotion quests can no longer block access to this quest.
Go to the Imperial Whitegate door at (L-9) for a CS and key item Imperial Missive.
The quest is not marked as active until this step is completed.
Make your way to Ru'Lude Gardens and have a CS through the Door: Audience Chamber at (H-6).
Curious readings from the chamber where the iron colossus sleeps have Imperial researchers ill at ease. At Her Majesty's behest, seek the support of the four nations for a plan to repair the colossus and free the Empire from its shadow once and for all.