This side-mission can be found by entering the Normandy’s galaxy map and having the ship travel to the following location:
Sigurd’s Cradle > Decoris > Sanctum.
Scan the planet and locate the anomoly to begin the mission.
As you land, a scene will play showing a guard running inside to get some mates. As such, you should immediately take cover as a group of 5-6 Blue Suns mercenaries will exit the building in front of you. A further group of 5-6 will emerge soon after followed by a third and final group of 5-6 enemies. Just about all these guys are the standard Troopers with the exception of a couple of heavy soldiers who will sit back and shoot rockets at you. Once the area is clear, grab the canister of Refined Iridium near the door before heading inside.
As you enter the building, take cover behind the glass wall directly in front of you and open fire on the Blue Suns in the room below. If they try to climb up the ramps to reach your level, do your best to eliminate them before they can do so and you should have no worries clearing out the room. When it’s safe, climb down to the bottom floor and check out the room behind the unlocked door to the right for a wall safe and a datapad . Return to the main area.
On the left side of the main room, you will find a closure message and the entrance to the next area. Cruise into the next room and turn left. Take cover behind the tables here as a group of Blue Suns Troopers will pour out of the tunnel at the back of the room. Once you have dealt with the hostiles and they have ceased coming, enter the tunnel the enemies came from.
In the tunnel, check the first alcove to the left for a canister of Refined Iridium . Continue along the main passage until it opens out into a large cavern. Check out the various bits and pieces lying around for three canisters of Refined Iridium , a data pad and a box of Power Cells . After picking the lot up, enter the door.
Turn left and descend the stairs for a scene. Afterwards you will have to defend yourself against a pair of YMIR Mechs. This can be tough as you have very little space in which to maneuver. Your best bet is to seek out the solid cover and use your party’s abilities as much as possible to take down their shields and armor before they get too close. Once they have been defeated, a named mercenary - Captain Narrom - and 8-10 Blue Sun s Troopers will enter the area from the same general location the YMIR Mechs came from. Finish them off the same way you did previously.
Either side of the locked door at the end you will find small ramps leading to a storage room. In the left-hand room you will find a wall safe and in the right one you will find a computer with a little back-story. Return to the main area and bypass the security on the locked door; overload the distress beacon control here to complete the mission.