Given Aloy's actions, all possible optional allies joined the defense.

Join a co-op session.

Use the UV Flashlight to kill a Viral.

Kill 20 enemies in a row with melee weapons without taking damage.

Activate your first Metro Station.

Activate your first Electrical Substation.

Activate your first Water Tower.

Lose the maximum level of Chase.

Perform 50 takedowns.

Modify your weapon for the first time.

Activate your first Windmill.

Enter the Bazaar.

Reach Villedor.