If you're unaware because you've spent 200 levels worth of XP looking for duct tape, the faction you decide to stay with will be who the Endgame faction is. Each faction has its own point of Endgame, but depending on how many you're in and your affinity with each respective faction will also affect this. The eligible factions are the main four - Minutemen, Brotherhood, Railroad and Institute.

Each will have its own unique world change and environmental outcome, however they're all similar in their own way and will not mean much overall.

If you're going for either Brotherhood, Railroad or Institute endgame, your decision during "Battle of Bunker Hill" will be a very large factor for your endgame.

Understand that I've done this while having a mutual relationship to the Minutemen on all runs, but I'll update the guide accordingly if I discover the other changes. Final Battles will also be included as time goes on.

Alternatively, you can simply kill Father atop CIT Ruins after you finish the battle if you want to immediately ruin your affinity with the Institute and go join whatever faction you want if you want to do it that way.

Ad Victoriam, Knights! The Brotherhood may be the only Major Impact faction due to the inclusion of Liberty Prime 2.0. Should you take the Brotherhood of Steel route for the Endgame, Brotherhood Soldiers may or may not be found in Diamond City, checkpoints may or may not be occupied, and Liberty Prime can be seen patrolling the Airport. Preston Garvey, Nick Valentine, Piper Wright, Curie and Cait may have unique dialogue where they either question or confront you about your decision.

Liberty Prime cannot be commanded like a companion, and you can get crushed under its feet. Also as a writers note, I played it with The Danse Dilemma downloaded. If anyone can tell me what its like without Danse before I discover it, please let me know and I'll update it.

Humanities Future. As the upcoming Director, you're given a choice by the Directorate on whether to focus on Synth Production, or Weapons Production. At the Endgame where you fight the Brotherhood at the airport, your choice will have an impact on how things occur.

Synth Production Route - More Synths (and maybe a courser) will relay in to assist you, but they will have basic Institute weaponry. The more the merrier, basically.

Weapons Production Route - Less synths will relay in to assist you, but they'll have heavier weapons, like Rocket Launchers. Power over power, basically. Note - These weapons are not unique Institute Variants and will never be seen being used by patrols ever.

Generation 1 Synths will be found without a chasis in Diamond City and will only speak specific phrases but do not engage in dialogue interactions. Nick Valentine and Piper Wright will sound upset, or even angry at your decision, and Preston Garvey will sound ever-so concerned but won't challenge your choice. Checkpoints will be monitored by Uniformed and Armored Gen 1 synths. You may also now have access to Synth Relay Grenades at Institute Equipment Requisition.

Ah the Minutemen. Every single settlement should've been helped at least once by now. After you finish the Endgame with the Minutemen faction, the many checkpoints [ex. Military Convoys, unlabled abandoned structures] will have Minutemen in them, and you'll see Minutemen in Diamond City. Nick Valentine and Piper Wright may have unique dialogue either confronting you or asking you about your decision.

The Synth's best friend. Should you be with the Railroad at the Endgame, checkpoints and Diamond City will be occupied by Railroad Agents and Heavies, and you'll also be given a repetitive RNG Location Quest in the form of needing to locate worker synths that escaped if you decided to take the route where you evacuate the Institute. Nick Valentine, Piper Wright and Preston Garvey may have unique dialogue either questioning or confronting you about your decision.

The Evacuation route is optional, though its recommended if you don't want Desdemona to be a little hard-ball with you in post-game dialogue> This route can also not be taken if Father is killed before the evacuation option can be executed