Mass Effect 3: Priority, Mars - walkthrough Mass Effect 3 guide, walkthrough

Last update: 11 October 2022

On this page of the Mass Effect 3 guide you'll find the walkthrough for the main quest called Priority Mars. Our guide explains where Liara T'Soni is located, how to defeat the Cerberus soldiers, how to avoid the defense turret, how to behave during the encounter with the Illusive Man and how to complete the chase after Eva.

• Reaching Mars and battles against Cerberus soldiers
• Encounter with Liara T'Soni and more battles with Cerberus soldiers
• Guardians and Centurions - first confrontations
• Decontamination protocols puzzle
• Avoiding the defense turret
• Tutorial - giving commands to team members
• Conversation with Illusive Man
• Chase after Dr. Eva

Reaching Mars and battles against Cerberus soldiers

Received from: Admiral Hackett [Normandy SR-2]

Unlocked by: Received automatically after completing Priority: Earth.

Head out of the ship and start exploring [Mars: Prothean Archives], eventually reaching a place where you can jump onto the lower level. Check out sergeant Reeves' corpse and take his sniper rifle [M-92 Mantis I], which you should set as your active weapon right away (upper left slot).

Head to the opposite direction and soon your will come across Cerberus Assault Troopers attacking innocent scientists. Get behind a cover and attack the enemies by surprise, not letting them alarm their buddies if possible. I'd recommend using the newly obtained sniper rifle here, though it's not absolutely necessary.

After the battle, continue onwards to the Martian complex. If the Cerberus Troopers managed to raise the alarm, you will come across another group after entering the compound. Just like before, stand behind a cover and don't let the enemies get too close.

Secure the area and head to the main entrance, where you have to interact with the elevator control panel. Inside the elevator, you will speak with your party members.

Encounter with Liara T'Soni and more battles with Cerberus soldiers

As the elevator reaches the new level, a cinematic with Liara T'Soni - who you can know from the previous installments - will start. Watch her deal with the Cerberus soldiers and speak to her (I'd recommend asking her about details of the device that's supposed to help in defeating the Reapers, though it's not absolutely necessary).

The conversation will be interrupted by the appearance of a new group of Cerberus soldiers. Also note that James has been removed from the party and Liara took his place [150 EXP].

The game will suggest using one of Liara's powers called Singularity and it would be worth to follow that advice (unless you're playing as an Adept yourself and have this power) [150 EXP], as the enemies can become easy targets thanks to it.

Use any method you like to deal with the Cerberus Troopers who appeared on the upper balcony, at best staying behind cover pointed by the game. After the battle [150 EXP], look around for a Med Kit [100 EXP] and the elevator control panel (the normal elevator is damaged).

Start climbing where the lift raised one of the machines. Jump onto the machine and from there onto the upper balconies. Head right and you will reach another door [150 EXP].

The game will suggest you try the surprise melee attack. Approach the marked cover and head right after sticking to it [150 EXP]. Stand beside one of the Cerberus soldiers and hold down F to execute him. Quickly deal with the others and don't let them get near Shepard (the rifle or powers that slow down/stop enemies might come in handy here).

Head to the neighbouring room. Look around for a Datapad [75 EXP] and enter the control room (Liara should already be there). Collect the ammo, armour part [Ariake Technologies Gauntlets], submachine gun [M-4 Shuriken I] and Med Kit [100 EXP]. In the end interact with the console to watch a video recording and unlock the further passage [150 EXP].

Head onwards until you reach and exit leading to the surface [150 EXP]. Use the ladder on the left to find a new armour piece [Kassa Fabrication Chestplate]. Head up the ladder, jump onto the neighbouring ledge and go through the open door to reach a dark room [150 EXP]. Start exploring this room and you will find a Datapad on your way [75 EXP].

Go down the stairs and note that the covers went down. The enemies can't see you, so you can attack them by surprise. What's more, you can either eliminate the whole group at once or wait until the conversation comes to an end and some of the Troopers leave this place.

Before you leave the dark room, look around for a weapon upgrade [SMG Scope]. Jump through the destroyed window and head into the environmental control, picking up ammo and interacting with the med station on your way [150 EXP].

After exploring the area, use the console. It will unlock access to the lab, start another cutscene and initiate a conversation with Liara [300 EXP].

Guardians and Centurions - first confrontations

Head to the transport centre. After reaching the new room, look around for the [SMG Ultralight materials] and consider using the weapon bench. Head up the stairs. Open the door, place your subordinates behind covers and start attacking the Cerberus soldiers in the distance.

During this fight you will come across two new types of enemies. The first type are Guardians who hide behind metal shields. The best way of eliminating them is using Biotic powers (Liara or Shepard) on them, though you can also try to shoot them with the sniper rifle.

Gradually fight your way through the consecutive rooms, remembering about choosing proper covers for all your party members. Also don't forget to check out the Datapad that you will find on your way [75 EXP].

In the further part the game will let you choose between two corridors. Personally I'd suggest placing your team members by the upper corridors and choose the lower corridors yourself to flank your enemies. You should notice that Centurions armed with shields will participate in this part of the fight. The best way of destroying the type of shields that they're equipped with is using powers like Overload, though you can also help yourself with other skills or grenades and special ammo types.

Decontamination protocols puzzle

Continue onwards until you reach a room with activated decontamination protocols. You will have to solve a puzzle connected with using two consoles, located to the left and right of the door. Those consoles control the sterilisers and you have to stop them so that you unlock a passage.

Head into the room and look for a Med Kit [100 EXP], Datapad [75 EXP] and two weapon upgrades: [Shotgun High Caliber Barrel] and [Sniper Rifle Extended Barrel]. Notice - in the case of the second upgrade, you might have to change the position of the sterilisers again. Once you're finished, create a passage to the door on the right (screen above) [150 EXP].

Avoiding the defense turret

Turn left, heading towards the control centre. There, you will be greeted by a security turret. It cannot be destroyed, the only thing you can do is avoid it, which is directly connected with hiding behind covers.

In accordance with the instruction, hold down W and afterwards SPACE to made Shepard run between covers (screen above). Notice - make sure to "aim" well at each cover and note let go of SPACE until Shepard hides behind it.

After reaching the turret room, you need to start going left. in this case you need to hold down A and only push SPACE (without holding it down). Additionally you have to press the middle mouse button after reaching a corner. Carefully continue onwards until you reach a spot where the turret cannot reach you anymore.

Enter the control room and take care of the Cerberus soldiers found there. They shouldn't cause you too much trouble, though you should look out for the Centurion, remembering about destroying his shields. After the battle, look around for ammunition, a Med Kit [100 EXP], Datapad [75 EXP] and weapon upgrade [Sniper Rifle Concentration Module].

Also in the end interact with the turret control panel, which will pay a new recording and cutscene picturing the Cerberus forces being outsmarted [150 EXP].

Tutorial - giving commands to team members

As you wait for the Cerberus forces to arrive, the game will offer you to test the option to give orders to your party members and if you haven't used it until now, it's worth to do it now and send your subordinates (Q and E) behind the marked crates.

I'd recommend keeping Shepard on the upper the upper floor or the leading to the ground floor. After the Cerberus soldiers arrive, start attacking them. Don't let them get close and especially look out while fighting the Guardians and Centurions. After the fight, head into the cable car together with your team and interact with its control panel [225 EXP].

Riding the cable car won't unfortunately go exactly as planned, as will get sabotaged. Note that a second car started coming your way and you should start shooting at the enemies inside as fast as possible. When the two cars are beside each other, I'd recommend switching to the shotgun and eliminate the others using it. Luckily you don't have to worry about them boarding your car. Afterwards jump to the second car and use its control panel.

You will have to fight again right after reaching the new location. I'd recommend ordering your team mates to leave the car as fast as possible and place them by the nearby covers, as the enemies will likely use grenades.

Just like before, try eliminating the enemies from a distance, remembering about the "elite" types of Cerberus troops. Also keep an eye on the areas where they used smoke grenades and make sure they don't surprise you. Having dealt with them, examine the area to find ammo, a weapon upgrade [Shotgun Shredder Mod], the [M-15 Vindicator] and a med station [100 EXP].

Conversation with Illusive Man

Head to the nearby door and try opening them, which will engage a few longer cutscenes. Most of all, you will "meet" the Illusive Man. Note that during the conversation you will be able to use a special dialogue option: charm (upper left) or intimidate (lower left). It won't change the Illusive Man's attitude in any way, but will let you gain more paragon or renegade points. In the end there will be a scene with doctor Eva, who will start running away upon finishing to download data from one of the computers.

Chase after Dr. Eva

In accordance with the game's hints, hold down SPACE to activate running mode and head after doctor Eva. Throughout the chase you should keep away from any elements of the environment, so that Shepard doesn't come up with the idea of taking cover. Also don't waste any ammo or use your powers, as you won't be able to stop the doctor prematurely in any way. After you reach the already explored room, open the door and use the console to lower the covers and continue the chase.

Further on you should try to avoid the probes left behind by Eva, even though getting hit by one won't kill you or even hurt badly. Soon enough you should see a ship with two Cerberus Troopers on board, who you can either kill or ignore and focus solely on the chase. The section will end only after you reach the landing zone.

Now you're in for a whole series of cutscenes. The only important part will be when you will have to finish off doctor Eva after the crash. Use the pistol for that and don't let her get near Shepard (it would cause instant death). Also note that you have (temporarily) lost one of your party members, either Kaidan Alenko or Ashley Williams. After reaching the Citadel, commander Bailey will ask you if you prefer going to the Council or visiting your wounded friend first. The choice doesn't really matter, as you will be able to make the choice on your own anyway, as the game won't automatically move you to the meeting room. You can move on to the Priority: The Citadel I main mission.

Prizes for completing the mission:

1. Mission unlocked: Priority: The Citadel I
2. New party member: Liara T'Soni
3. [35000 credits]