Atom's Bulwark

Atom's Bulwark is a unique piece of armor in the Fallout 4 add-on Far Harbor. It is a legendary arm or chest piece of Marine armor.

Gameplay
It has a unique legendary effect which provides a Damage Resistance and Energy Resistance of 15 at 0 Rads, in addition to the resistance provided by the armor. They both increase linearly according to the following: for every 100 Rads the player character currently has, their total DR and ER will both increase by 5. Specifically, if 10% of their health bar is taken by radiation, they will gain 5 DR and ER. If 90% of their health bar is taken by radiation (900 Rads), they will gain 45 DR and ER for a total of 60.

The specific form of this item depends on the player character's level: below level 40, it spawns as either a left or right arm; above level 40, it spawns as a chest piece. Note that these items are generated dynamically, as their Form ID starts with "FF".

Location
Rewarded by visiting High Confessor Tektus after completing Reformation or after destroying Far Harbor in Cleansing the Land.