Suicide MissionEdit
Before launching the Suicide Mission, make absolutely certain that you have purchased the armor, weapon, and shielding upgrades for the Normandy, as for each one of these not purchased a squad member will die during the run to the Collector base.
The following list shows, in order of preference, which crew member will die if you haven't upgraded that part:
Heavy Ship Armor: Jack
Multicore Shielding: Kasumi, Legion, Tali, Thane, Garrus, Zaeed, Grunt
Thanix Cannon: Thane, Garrus, Zaeed, Grunt, Jack, Samara/Morinth
Note: This tier is sorted by the characters' order of dying in descending order. Squad members on the "Multicore Shielding" list will not die if they are in your party when you fight the Oculus. Bringing party members to fight the Oculus will not protect Jack if you do not have Heavy Ship Armor, or anyone on the "Thanix Cannon" list.
After entering the Omega 4 Relay but before the beginning of the suicide mission, your ship will be attacked by an Oculus at two different intervals (between cutscenes). You will be taking in a team to fight the Oculus, though the team selection does not have any consequences or impact on gameplay, thus you may choose anyone you want.
There are three stages to this mission, during which you must select members of your team to perform certain duties. Choosing an inappropriate character for those tasks will result in someone's permanent death. Appropriate choice are listed after Ideal, while inappropriate choices are listed after Non-Ideal.
Note: If an ideal squad member is not loyal for your playthrough, consider them to be a non-ideal choice.
If at the end of the final battle only one or no squad members survived, no one will help Shepard onto the ship, resulting in the Commander's death. A single surviving squad member is not enough to save Shepard.
Collector Base: InfiltrationEdit
Main article: Collector Base: Infiltration
A Specialist Technician is required to infiltrate via the station's vents to bypass the defenses and doors then open the central gate for the rest of the squad.
Ideal: Tali, Legion, or Kasumi.
Non-Ideal: Anyone else, or a disloyal technician, as they will be shot in the face while forcing the door shut.
A Fire-team Leader is required for the second team. The briefing conversation mentions that this member must be experienced in leading a team.
Ideal: Garrus, Jacob, or Miranda
Non-Ideal: Anyone else, as they will get your specialist technician killed, even if a loyal Tali, Legion, or Kasumi was chosen.
Your Team – will be fighting against Collector Drones, Harbingers, and several Collector Assassins, all of which have biotic barriers on harder difficulties (Drones gain barriers on Hardcore and Insanity only). Characters with Warp, Incinerate, and Concussive Shot powers are a good choice. Warp and Concussive Shot are effective at taking down biotic barriers. Warp and Incinerate deal damage against armor - with Incinerate dealing decent damage against organic enemies along with setting them on fire for a few seconds, and it does some damage against barriers.
Miranda, Grunt, Samara, Zaeed, Garrus, Thane, and Mordin are all good choices since all of them posses either Warp, Incinerate, or Concussive Shot which are good powers to have for this segment. Samara can unlock Reave, which is a lot like Warp except it can heal Samara and give her a temporary health bonus, not to mention it can damage a Collector standing behind a guardian shield.
You will need to fight several Collector squads, while pressing forward to activate eight different consoles alongside a path beside the vent in which is your Specialist. The heat in the tunnel will kill your Specialist if you take too long to reach the consoles, so you should clear out the enemies as quickly as possible. Another tactic (although it might require a few tries depending on your skill level and the difficulty setting) is to ignore enemies and simply rush ahead opening all the consoles in your way. Also, while the Collector Drones fly in to engage your squad, they are highly vulnerable in mid-air to Throw and Concussive Shot. In normal difficulty, this will instantly kill the Collector Drone and Throw Field can take out an entire group before they get a chance to attack you. It is advisable to save your game before you press the last button in case you select the wrong character for the next session. The mission ends immediately once the final button is pressed, so if time is near to running out completely it may be worth it to ignore any remaining enemies and simply run to the button and press it.
Collector Base: The Long WalkEdit
Main article: Collector Base: The Long Walk
A Biotic Specialist to generate a shield, protecting the squad against Collector swarms.
Ideal: Samara/Morinth or Jack.
Non-Ideal: Anyone else. Doing so will result in one of your squadmates being carried off by a Seeker swarm.
A Fire-team Leader for the second team (referred to by Miranda as "the diversion team").
Ideal: Garrus, Jacob, or Miranda. Note that Miranda will not die here even if disloyal.
Non-Ideal: Anyone else. There is a possibility of this leader dying as the doors close at the end of the long walk (shot in the stomach as the door closes).
Note: Even if you choose an optimal candidate, they may still be shot (and play the same initial animation). DON'T PANIC, they will survive the injury. This is confirmed when Shepard comes to their side and they remain standing.
An Escort to guide the Normandy crew back to the ship. However, you can't use this person for the final battle. Choosing no one results in the death of the Normandy crew.
Ideal: Mordin. This will ensure his survival because he has a strong chance of dying if he doesn't escort the crew back, even if he is loyal. Otherwise, any loyal squad member is guaranteed to successfully escort the crew back to the ship.
Non-Ideal: A team member that you have not secured loyalty from. This squad member will perish while escorting the Normandy crew. Also, a squad member with a high "defensive skill" value (Grunt, Zaeed, Garrus), as this may indirectly cause Mordin's death if he is left to hold the line.
Your Team – You will be fighting against Drones, Harbinger, Assassins, waves of Husks and Abominations, and a Scion.
Tali and Legion are probably preferable for this segment; their combat drones can escape the biotic field safely and root out any dug-in enemies.
Another strategy might be taking some good damage dealers. Jack, Zaeed, Grunt or Thane will do much more damage, especially important for husks!
Your chosen Biotic Specialist will erect a dome-shaped biotic shield encapsulating the squad from Collector swarms. Note that moving outside of the biotic barrier will cause damage to Shepard and eventually result in death. The Biotic Specialist will move slowly through the level and stop three times for you to fight off a wave of enemies before proceeding. The waves encountered are:
Drones and Harbinger - on the far side overlooking a small pit with a large block in the centre.
Husks and Abominations climb up from a ledge then Drones, Harbinger and Assassins will fly in - on a long walkway with a left-facing 'sniper alley'.
Husks, Abominations, and a Scion - at a left-turning bend in the road with a raised platform on the left side.
Final Battle Edit
Note that, while manual saving is not allowed from this point onwards, the game will auto-save at the beginning of each part. Loading an auto-save also gives you the opportunity to change the weapons loadout of your squad. If you die, you will have full ammo when you reload the game, even if you didn't have full ammo at the last save.
Part 1 – Team Selection
The team you select here will be with you for the remainder of the suicide mission – you will be fighting against Drones, Harbinger, Assassins, Abominations, Scions, and one giant Human-Reaper larva.
Ideal: Squad members who are loyal to you and are less suited for defensive tasks such as Mordin, Jack, Kasumi, and Tali.
Non-Ideal: Squad members who are not loyal to you. They will die after the battle as the Collector station begins to fall apart.
Note: The teammates you do not choose are automatically assigned to hold the line against the Collectors. A 'defensive skill' value is calculated for the 'hold the line' group as a whole, based on a defensive value inherent to each character. Loyal characters gain a bonus to this value. If the 'defensive skill' check is not high enough to ensure all characters' survival, squad members will be designated to die based on their vulnerability, with Mordin taking priority if he is present. Leaving behind strong defenders, such as Grunt, Garrus, and Zaeed will increase the group's odds of survival. In contrast, certain characters such as Jack, Tali, and especially Mordin have less skill in holding their position and should be removed through escort duty or taken along. The entire group will survive as long as the combined defensive skill is high enough, otherwise the game selects a squad member to die based on the scenario of who was left behind and how loyal are the group members. (Squad members who are not loyal are most likely to survive here than anywhere else, provided the group's collective defense skill is high enough, although they will be the first to die if the skill is not.) Leaving behind two strong defenders such as Garrus, Grunt, or Zaeed should suffice, provided you haven't lost too many people.
Note: The order in which squad members die is as follows: any non-loyal squad members, Mordin, Tali, Kasumi, Jack, Miranda, Jacob, Garrus, Samara/Morinth, Legion, Thane, Zaeed, Grunt