All of the decisions and choices made in Mass Effect 1 and 2 led to this. Mass Effect 3 marks the final showdown with the Reapers, and if you’ve accumulated war resources during the Legendary Edition, they’ll come into play at the end. Of course, during the third title you have the opportunity to make even more effective decisions – here are all the big and small decisions with their consequences.
Diana Allers- Diana is found in the Citadel on your first visit to Normandy Dock: Bay D24. You can have her as an embedded journalist on the Normandy and she becomes war capital too (although she can be told to leave anytime). If rejected, Diana goes to SSV Shasta and dies when the ship is later destroyed.
Virmire Survivor on Mars – You will meet the Virmire survivor on Mars who, depending on your choice from Mass Effect 1, could be Kaidan or Ashley. If you mainly choose Paragon options with them on your squad, they will have a more positive attitude towards Shepard. Go for Renegade options and they will become less trusting. Given that Ashley / Kaiden becomes a ghost and works under Udina (who betrays the Citadel to Cerberus), the renegade means that they could potentially die in this scenario.
Grissom Academy – The “Grissom Academy: Emergency Evacuation” mission becomes available to Thessia and sees Shepard reunite with Jack. It can expire if you don’t complete it before Priority: Citadel 2. It is therefore recommended that you do it and receive Jack and her students as war items. You can also choose how you use them – send them to the front lines and they will die. Keep them as support and they will live. If the mission is not completed, Jack will be transformed into a Cerberus Phantom and will appear at Cronos Station where she must be killed. And no, their students don’t survive either.
Tuchanka – This mission culminates in an attempt to heal the genophage by scattering him through the cloth on Tuchanka. However, you will be informed by the salarians that the cloth has been sabotaged. If you bring this up with the krogan, the remedy will be distributed as usual.
If Wrex is alive and you have received Maelon’s data in Mass Effect 2 (more information on this here), the STG doctor present will try to fix the sabotage. You then have the choice of stopping them, resulting in weakened krogan support and more salarian support, or having them repaired, which results in the total loss of salarian support. If Wrex died in Mass Effect 1 and Maelon’s data was not saved, the STG doctor can be persuaded to aid the sabotage, thereby ensuring the support of the Salarian and Krogan (although the latter will be weaker than normal). If Maelon’s data is not saved, Eve will not survive the process.
Meet Miranda – Miranda will show up at some point and may later be a war asset. First, read about Kai Leng in your private terminal, then warn her about him on your first conversation (especially if you haven’t won their loyalty in Mass Effect 2). Give her access to alliance resources in the second conversation. If you romanticized Miranda in game two, you can’t cancel it. Complete all of these steps and she will survive and become a weapon of war. Fail and she will die.
Attican Traverse: Krogan Team – In the mission “Attican Traverse: Krogan Team” you will meet a Rachni leader. If you’ve spared the Rachni Queen on Noveria in Mass Effect 1, she’ll appear here, otherwise it’s a Rachni breeder created by the Reapers. The protection of the Rachni queen leads to her joining the war effort. Killing the Rachni Queen in Mass Effect 1 and then helping the Rachni breeder will result in her cheating on you and reducing your overall war fortune. You can also choose to kill the rachni queen or the breeder, which is highly recommended in the latter case (you won’t get any assets, but at least none will be lost). It’s also worth noting that Grunt can take part in this mission but will die if you haven’t completed his loyalty mission in the previous game.
Kallini: Ardat Yakshi Monastery – If Morinth is kept alive in Mass Effect 2, there will be a report on her in this mission. Otherwise, if you go with Samara, then she will play a big role. In the end, while Falere is present outside the monastery, Samara will quote the code of justice and, unable to kill her daughter, attempt suicide. If you stop her with a Paragon prompt, she will join as war capital while Falere stays in the monastery.
If Samara dies or is absent, you can leave Falere on the planet (where she promises she won’t be alive when the reapers arrive) or kill her.
Priority: Rannoch – It is imperative to previously rescue Admiral Koris in the mission “Rannoch: Admiral Koris” using either Charm or Intimidate. Make sure you also complete the mission “Rannoch: Geth Fighter Squadrons” before doing Priority: Rannoch. This allows the fighters to be deployed and both Legion and Tali to be alive. If you don’t, either Tali and the Quarians will die if you allow uploading or Legion and the Geth will die if you stop uploading.
Kelly Chambers’ Identity – Kelly Chambers is in the Docks: Holding Area in the Citadel on your first visit, assuming she survived Mass Effect 2. You can tell her to change her identity, which will be crucial if Cerberus attacks the Citadel, as it will give her a chance to survive. When she meets her again, she’ll confess that she spied on Shepard and the crew for the Illusive Man. If you say “It’s already in order”, Kelly will return Shepard’s fish from Mass Effect 2.
Aria’s Speech and Petrovsky’s Fate (Omega DLC) – Depending on your actions in the Omega DLC, Aria’s attitude will be different and this will be reflected in her speech. If you haven’t followed Paragon or Renegade consistently, you will be given two dialogue options: “You need to reform” and “I’ll let you guess”. The former is a Paragon choice while the latter is Renegade – both can directly influence the content of their speech.
If you were mostly renegade during the mission, Aria will kill General Petrovsky. The latter can be saved as a Paragon and even if Aria is not ready, there are two Paragon interrupts that make this possible. Aria won’t be very happy with the result, so keep that in mind. If General Petrovsky Shepard is extradited, they can kill him with two renegade interrupts.
Brooks’ Fate (Citadel DLC) – Once the final boss of the Citadel DLC is done, you need to determine what happens to Agent Brooks. If you choose the Paragon dialogue choice and interrupt Paragon, Brooks will accept their fate and not try to chop the handcuffs to escape. Select the renegade dialogue option and Brooks chops the handcuffs through to escape. You then have the option to shoot them with a Renegade prompt – this can also show up if you don’t take over the Paragon interrupt from earlier. If you don’t shoot Brooks, a teammate will shoot her instead, bringing the story to an end.
Illusive male conversations
The Illusive Man is an important part of the finale, but depending on the dialogues chosen in the conversations in Mass Effect 3, you can help prevent Anderson’s death. You will speak to him at Mars, Thessia, and Cronos stations before the conduction takes place on Earth. The key is to use every possible option to bewitch or intimidate in these conversations. Some will only be found if you select “Investigate”. So make sure to thoroughly examine each dialogue option.
If you have successfully used all charm options, the “But you already have that” dialog will be available in the conduit. This will convince the Illusive Man that he has been indoctrinated, which will result in him committing suicide. If you choose to use all of the intimidation options, you will get the dialogue option “Then you have failed mankind”. If you choose to do this, the Illusive Man will push Anderson aside and aim at Shepard, delivering a call to renegade. Use this to kill him – failure to do so will result in Shepard’s death and have to repeat the conversation.
If in previous conversations you have not used all of the charm and intimidation options, you only have two dialogue options: “You are theirs now” and “You are pathetic”. If you go with both of them, the Illusive Man will kill Anderson. You will be given a message to the Renegade to kill him first – if you don’t ingest it, Anderson will die. A second prompt will then appear to kill the Illusive Man. If you don’t use it, Shepard will die and the conversation will restart.
If Anderson survives, he will have one final conversation with Shepard. When Anderson dies, Shepard will look down at Earth one last time before heading out.
Effective military strength and ends
The end is determined by your war ability and your effective military strength (EMS). With the Legendary Edition, all of your decisions in the trilogy are taken into account, so the total number is slightly higher than in the base game. You can find more information about the different endings of each game here.
For simplicity, let’s look at the EMS requirements and results from the original version. At less than 1,750 EMS (aka the lowest possible value), only the Control and Destroy extensions will be available, and the toll from that is very high. If you have 1750-2649 EMS (Low-Mid) you have the same ending options, but the Destroy ending is less brutal.
At 2650 to 2799 EMS (a medium EMS amount in the Legendary Edition) the same two options are available, but neither will cause damage and the Normandy’s crew will survive. From 2800 to 3099 EMS (medium-high) you have the synthesis option along with control and destruction, which does little damage. At 3100 EMS or higher, which is 7800 or more in the Legendary Edition, you can choose any ending with no major consequences and Shepard will end up being teased as alive.