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Z4K-97B is a synth living in the Commonwealth in 2287.


They are a hostile synth encountered in the Institute's reactor room during the quest The Nuclear Option with any faction. Z4K-97B, along with A-2018 and XPN-20A, will serve as the game's final boss during all endings other than the Institute ending.

Interactions with the player characterEdit

Interactions overviewEdit

Perk empathy synthesizer
This character is involved in quests.

The Nuclear Option


Apparel Weapon Other items On death
Synth uniform Institute laser Reactor terminal password


  • Z4K-97B wears a special variant of the synth armor which is jet black in color and can be shot off by focus fire and explosives, much like power armor.
    • XPN-20A and A-2018 wear identical sets of this unusual armor.
    • Said armor cannot be obtained via looting, pacify trading/armor swap, companion inspecting, etc.
  • Z4K-97B will always spawn as a legendary enemy.


Z4K-97B appears only in Fallout 4.

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