Settler (Fallout 4)

A settler is any person who decides to join a settlement. They can be found all over, especially near settlements.

Interactions with the player character

 * Able to trade.
 * Able to equip gear, including grenades.
 * Assume a trade roll when assigned as such.
 * Can give player radient/repeatable quests, which commonly involve exterminating nearby Ghouls, Raiders or Super Mutants. Or to deal with a kidnapping.
 * Can pointlessly sell traded items back to the player
 * Killing one will agro the whole settlement if not done subtly.

Settlers in allied settlements
Speaking to a settler from one of your settlements will allow you to access their inventory and select their equipment much like you would a companion. They can be armed with better weaponry than their pipe pistols, and they don't seem to consume ammunition. All the same, they only need to have one unit of ammunition of the type their gun uses in their inventory to be able to fire their weapon, then, they can fire at will and not consume any ammunition. This does not work for the missile launcher or Fat Man, as these are tagged with "NPCs Consume Ammo". The same holds true with grenades.

Settlers assigned as shopkeepers have additional dialogue options when spoken to similar to other merchants. Select "trade" from the dialog tree to access their inventory. Speaking to a shopkeeper settler outside of their operating hours will go straight to their personal inventory as normal. Doctors seem to be an exception. A settler assigned to a doctor stand will not have a trade dialogue option when spoken to during business hours. To access their inventory, either wait for the shop to close or unassign and reassign them from/to their shop.

Settlers assigned to a guard post will man that post, as well as up to two other unmanned guard posts. They will walk in a circuit between such posts, making it pragmatic to place groups of three in relatively close proximity. They rarely leave these posts, to the extent that they do not sleep when the player is visiting (like any settlement resident, they still require a bed).

Unassigned settlers default to gathering any unassigned crops. Assuming the player is present, these settlers as well as those assigned to a Scavenging station will patrol the settlement when not working, and if chairs are present will periodically stop to sit and eat. Thus, strategic placement of chairs will allow these settlers to assist in monitoring a settlement's perimeter for intruders.

Appearances
Settlers appear only in Fallout 4.