Mass Effect 3

Story related. If you want more info, continue reading. Otherwise, know that this will unlock through the natural progression of the story.

Mission – Priority: The Citadel II
Acquisition - Automatic after completing Priority: Tuchanka.

This mission becomes available after completing the missions on Tuchanka and the mission investigating the missing krogan team. The salarian ambassador, Valern, will contact you, believing that Udina is up to something. When you arrive at the Citadel, it is under siege by Cerberus.

Insanity Tips:

• You’ll deal with the usual Cerberus troops, but with one addition, the phantom. They are not fun to deal with. If you ever wondered what a 22nd century ninja would be like, you will have your answer. They strike quickly and sometimes from behind. Your best bet is to keep moving around when they are present. Staying in cover means probably death since they come up behind you and melee attack you. They need to get close to you to do the most damage, so keep away and wear down their barrier and health from a distance.
• The hardest part of this is the elevator. I know I just said to not stay in cover when phantoms are present, but stay in cover and take out the assault troops. Let your squadmates occupy the phantom while you take down the troops or take out the power conduits on the other elevator.