Land on the planet and if you have any ammo modifiers (Cryo, Armour-Piercing etc), then activate it on all the weapons you’re carrying before moving anywhere (there’s a lot of guards to kill in this mission).
Run forwards and then in the hallway, look in the corner for salvage that doesn’t have any graphics (for some reason), but rewards you with 2,500 Credits for picking it up anyway! There’s a guard to your right, so pop his skull wide open and the battle will begin .
Note: When you’ve killed enough enemies in a wave, you’ll hear them shout out something distinctive; this is them retreating to the next objective area, so approach that area with caution.
To the Control Room
Inside, set a teammate up to cover the left flank, and outside, set someone up to cover the central open area (using the left barrier). You can run around to the wall that provides overlooking cover straight into the middle of the open area, allowing you to pick off troops stupid enough to come right at you.
Keep going until enough men are killed that they retreat back to the control room (up the ramp); before you head in, look to the right of the ramp and beside the ladder there’s ammo and salvage you can scan for 3,000 Credits . Run around to the back of the control tower, where there’s a ton of ammo as well as some Armax Arsenal Gauntlets to pick up near the ammo at the back of the room.
Secure the Control Room
Run up the ramps and use close-mid range weapons in here, use the top of the ramp as cover and pick each target off one at a time. Only go in when Shepard gives the all clear. There’s a Medi-Kit up here, along with Old Grid Schematics on the left side of the front-most control panel. Picking these up will allow you to complete the Citadel: Improved Power Grid side mission. When you attempt to activate the control panel, it’ll be cut off.
Re-activate the Power Grid
If you’ve got a sniper rifle handy, dash straight outside and look up to your right for a Nemesis and a Centurion dropping down onto the pipes. Line up that Nemesis’s head and give her the good news right between her eyes; do the same for the Centurion as he slows down when attempting to land on the ground below.
Stay in the doorway and place one member behind the wall panel at the very top of the ramp, and the other should stay inside the control panel, behind the window (as there’s cover there). If you need more ammo, you can simply drop down the ladder to your left and climb back up again.
It’s another case of settling in and wearing the enemy down, picking off the Engineers, then Centurions and finally the Assault Troopers. When you hear them fall back, restock up on ammo and then go back to where you landed at the beginning of the mission.
There are two power grids in here that are guarded well; get a few grenades in there first to soften them all up, then pick them off with close-range weapons. Shoot the locks on each of the two power grids to open them, scan them and get ready for a heavy fight back to the control room.
This is where Cerberus will send out more enemies for you to face, including the addition of multiple Guardians and additional Engineers. But stick to the same tactic as at the beginning; have both of the team guard the left flank, so you can then hang back and pick off the rest (preferably with a long-range weapon of death).
Keep plugging away (using biotic power combos where possible), and you’ll eventually find them regrouping back in the control tower. Just repeat the same manoeuvre as before and hit them from behind. Activate the guns now to complete the mission. You’ll be rewarded with +5 Reputation Points and 10,000 Credits.