Aeternus

Aeternus is a unique weapon in the Fallout 4 add-on Nuka-World.

Gameplay
Aeternus is a unique Gatling laser that bears the Never ending legendary effect. Although it uses the "Never ending" effect, its actual effect gives the weapon true unlimited ammo. It will use a portion of a fusion core when first fired, but the core's charge will not decrease again while using Aeternus.

Variants

 * Gatling laser - The common variant found throughout the Commonwealth.
 * Final Judgment - wielded by Elder Maxson.

Location
Carried by the rogue knight during the quest Amoral Combat. The quest must be repeated until the rogue knight is the challenger. Upon their defeat, they will drop Aeternus.

Related quest

 * Amoral Combat

Behind the scenes
The weapon's name is from the Latin language, meaning "eternal" or "immortal."

Bugs

 * Consumes 33% of a fusion core on the first shot, then nothing for the rest of its use. If the gun is put away or switched, it has a new fusion core automatically inserted which takes another 33% of the cores charge on its first shot. This can leave a regular user with a large stack of fusion cores with only 67% charge. Once the player is out of full-charge fusion cores the gun will automatically load the partially depleted cores, which will then fully deplete the fusion cores, though they still function in the gun.
 * To fix this, keep all but one fusion core stashed on a companion or in a container.
 * It seems to be irregular in consuming ammo. Sometimes draining a fusion core entirely in the first shots, or firing only as many shots as the player has fusion cores and then removing one core entirely.
 * Used cores randomly deplete to under 10 power then switch to a new core. As the ammo counter shows how many cores one has this is misleading as it gives the appearance of having infinite cores, until one sees all their cores have anywhere from 3-9 uses left.
 * After killing the rogue knight, it is possible they drop a random legendary item.
 * This can be avoided by forcing the rogue knight to exit their power armor, pacify and then fire at them, they will now be using the weapon, however it may not be legendary.
 * If the user has one or two fusion cores in their inventory, Aeternus will fire off one or two rounds before fully depleting the equipped core. If one has at least three fusion cores, the fresh loaded weapon will almost drain the equipped core completely on its first shot, after that it will reach "unlimited ammunition", consuming no charge afterwards. This is valid up until one loads a new fusion core either by equipping another weapon, modifying the Aeternus in a weapons workbench, or increasing the amount of fusion cores in one's inventory.