These are planetary missions involving Cerberus and mainly can be taken from Specialist Traynor standing near the Galaxy Map.
Mass Effect 3 N7 Missions Walkthrough – Galaxy At War
N7: Cerberus Lab
You should talk to Traynor to initiate this mission. You can find him in the lab in on Sanctum in the Decoris system. The waves of enemies you will face will get tougher with time so make sure that you stock up on ammo before the next wave arrives.
When Cortez goes away, you need to hold the ground on your own. Use the strategy according to the type of foe you are facing. For example, deal with the engineers before they can deploy the turrets and use biotics against the shield holders to weaken them.
You will have to defend (three to four enemy waves) until Cortez comes back, and you manage your escape.
Grissom Academy: Emergency Evacuation
After Traynor mentions the Academy, head to the Perta Nebula Cluster. Depending upon the decisions you made in Mass Effect 2 for jack, the mission can vary slightly. A couple of Cerberus soldiers waves attack you as you move on towards the objective.
You can use the generators in the room to cause some extra damage. Next, pick up the M-22 Evisceratir from the bench and then save Riley’s sister.
After you are done chatting with Jack, more enemies will arrive in entertain you. Deal with the tougher foes first and then switch to the weaker ones. After each wave, don’t forget to loot the area and also check the surrounding rooms in the area for any useful items.
Difficulty level of each next wave will be more difficult. Things will go crazy when engineers arrive with the turrets along with the guardians. If you are overran by the enemy number, then it’s always a wise option to retreat and seek cover.
In the next section, steal the Atlas for your own use from the engineer. Although the cannon requires you to stay static to fire, the weapon can come in really handy as a couple of well-placed shots can take out the enemies.
You will have to deal with a few more frantic enemy waves (stick to the basics) before you can collect your rewards at the end of the mission.
N7: Cerberus Attack
You can get access to this mission after completing Sur’kesh Deal with the first wave and then explore the area for all possible loot you can get.
After gathering the resources, hit the console for the next enemy wave. There will be a variety of foes in each enemy wave so you should diversify your style and try to deal with the tougher enemies first.
There are also multiple ways in which you can use your squad mates to draw the enemy fire so if one strategy does not work for you, shuffle the plan. After you complete the mission, you will get 50 point bonus to the Krogan First Division War Asset.
N7: Cerberus Abduction
You can initiate this mission from Traynor (after) either by helping Turians on Tuchanka or dealing with the Rachni.
The fight will be a regular wave after wave attacks with each wave tougher than the previous one. Try to hold the position where chances of being flanked by the enemy are least.
When Cortez arrives in pick you up, it’s time to loot the area for any useful items before you leave.
N7: Cerberus Fighter Base
When you are done with the problems on Tuchunka, you will be able to access this mission. There is nothing new in this mission except for the same-old horde style fights with the Cerberus. There will be plenty of enemies in that room so don’t hesitate to use your special powers.
The last wave will be most annoying, including engineers with Turrets and the Snipers. Try to stun the turrets and take out the snipers quickly. Deal with this wave to collect your mission reward.
To be updated!