This is the timed side mission that you will have received after completing the Extract Turian Survivors side quest. Head back to Tuchanka to begin. As you begin your descent, you will hear the real reason for the turian’s urgency in this situation; the bomb is actually of turian creation, designed to kill the krogan if ever a cure to the genophage were to manifest itself. Now Cerberus has discovered the bomb, and they’re out to detonate it to foil you in your attempt to kill the Reapers, as the krogans would never agree to the summit if a bomb of turian origin erupted on their planet.
As you land, artillery will pepper the landscape with explosives. Don’t worry about avoiding any of them, as they can’t hit you. Just watch out for Cerberus patrols, who will fire at you through the smoke and smog of the explosions. Kill all of the soldiers here to stop the artillery fire and advance. Look to the left to find the M-29 Incisor Sniper Rifle leaning on a wall. Climb up the ramp here to collect the Shotgun Blade Attachment. From here, head to the right. You will encounter more Cerberus troopers up here. This battlefield will be split into two vertical sections by a wall running through the middle. Cerberus will have set up various electronic shields to take cover behind along the sides of the path. Three will also be a turret accompanied by a Combat Engineer down the right side of the path.
You should try to take out the Combat Engineer first. Take cover behind the first electronic barrier, but beware, as Cerberus can destroy your cover with prolonged fire. Use a Sniper Rifle to shoot the Combat Engineer before he can cause any more trouble for you, and then focus on taking down the turret. Once you have gotten your use from the electronic barrier, move forward and shoot the generator to deactivate all of the barriers, rendering most of Cerberus’ cover useless. Alternately, if you want to get in close, you can rush down the left side of the path and use Biotic Charge and a Shotgun to close the distance between you and the Combat Engineer before finishing him off. From here, pop a Tactical Cloak or take cover to avoid the turret fire. Destroy the turret, focusing your whole squad on it if necessary, and then destroy the generator.
After the battle, search the right side of the arena, in the corridor where the shields were, to find the Rosenkov Materials Gauntlets. Follow the path towards the next area. Along the way, stop by the console and examine it to get 5,000 credits. Continue onwards, climbing up and over the rubble. As you climb over the last piece of rubble, look straight ahead to find the SMG Heat Sink Mod. Turn to the left to encounter more enemies. Simply shoot past this initial force, as there won’t be many soldiers here, and run forward. You will hear a Cerberus Captain telling his men to retreat. Grab the Pistol Scope and a med kit from the crates in front of you and proceed onwards. Drop down the ridge to the lower level. You will find several Cerberus troops packing a dropship in preparation for retreat. Shoot the shield generator to knock out their shields before picking them off. Grab the datapad in their encampment and restock your ammo at the nearby cache.
Keep moving down the linear path, picking off the bits and pieces of the Cerberus army who will remain behind. None of these groups will be large enough to pose a threat or demand any particular strategy. When you reach the end of the path, you will see the giant, crablike bomb protruding from the ground in the distance. Climb up the ladder to the right, grab the Sniper Rifle Concentration Mod on top of the crates and the Pistol Melee Stunner behind the second crate, and run towards the bomb. You will find one more group of Cerberus soldiers to deal with here before you can reach the bomb. Take cover and take aim at the Combat Engineer. He will have created a turret already. Kill the Engineer, and then his turret, and then shoot the remaining soldiers. Examine the crates behind where Cerberus was entrenched. You will find the Turret Control Schematics and a med kit. Proceed forward to reach the bomb at last.
When you arrive, Victus will be trying to hack the terminal to take control of the bomb. As he does, his two guards will be shot. Cerberus has found you. You will have to protect Victus while he hacks the terminal. Head down from the bomb platform and run to the left to proceed to the arena, where Cerberus will be sending their troops. A number of dropships will fly down and drop troopers into the battlefield. Some of them will drop Centurions. If you see one of these powerful soldiers dropping down, don’t hesitate to toss a Grenade or another powerful area-of-effect attack at the ground right as they land. Killing the enemies before they can even have a chance to attack is the best strategy in this battle. Allowing Cerberus to drop too many soldiers from their dropships is an easy way to get yourself flanked.
You will know that Cerberus is getting desperate when they airdrop an Atlas mech onto the battlefield. The Atlas will try to launch missiles and cannon fire at Victus, so keeping it distracted is priority number one. Focus your squad’s fire on the Atlas, even as more footsoldiers rush in to assist it. If necessary, try to kill the pilot and assume his place in the mech. Otherwise, weaken its armor with Biotics and follow it up with powerful weapons attacks or a Biotic Charge, Nova, and Shotgun combo. When the mech dies, carefully search the area for surviving Cerberus soldiers. They will continue to attack Victus as long as even a single one remains. When the last soldier is dead, a cutscene will play and Victus will attempt to disarm the bomb. Unfortunately, it won’t work. The bomb counter will begin. The only way for Victus to stop the countdown is for him to separate the power source from the bomb, which he will do at the cost of his life.
Return to the Normandy to find Victus and the turian diplomat Wreav fighting. Settle the argument and either console Victus or chide him for not telling you the truth in the first place.