Fallout 4 legendary weapons

Legendary weapon effects are effects applied to basic weapons that use special prefix modifiers that cannot be obtained elsewhere. Legendary weapons cannot be scrapped, but can be modified and traded with vendors. They will appear on screen when picked up, and are marked with a star. Unlike unique weapons, they are randomized and are never named. Legendary effects can provide the same effects as unique weapons; a "Relentless .44 pistol" is identical to Kellogg's pistol. Like unique weapons, Legendary weapons can be given a custom name and modified at a weapons station.

Legendary weapons are only found on the bodies of "Legendary" variants of enemies. They can spawn at random locations throughout the Commonwealth, depending on the difficulty setting. They are much more difficult to defeat than regular enemies, as each one has a chance to "mutate" after their health is depleted, restoring it to full and boosting their stats. They will almost always have a legendary piece of equipment in their inventory.

Legendary effects can be added to items through the console by following the next steps:
 * 1) Drop the item on the ground.
 * 2) Pick up the item in the air by holding E (how you would normally drag ragdoll and other objects around).
 * 3) Open console and enter "GetPlayerGrabbedRef". This returns the RefID of the item you're holding in the air.
 * 4) Take note of the returned RefID.
 * 5) Look up the ModID below for the desired legendary weapon effect, note it as well.
 * 6) Enter the following in the console (substitute the appropriate RefID and ModID):
 * 7) For example, you would enter in something like this:.
 * 8) The item will drop to the ground, and when you go to pick it up, you will get an overview similar to the one you get when you pick up any given legendary item for the first time.

As a simpler alternative to points 2 - 4 you can simply left-click on the item when it is lying on the floor. The RefID will then be displayed on-screen just as if you used the mentioned console command. Bear in mind certain weapons can be unusually challenging to left-click when dropped, so if this is unsuccessful, use instead.

You can't stack several mods on a single item, but you can replace a mod with another one via the console.

Legendary weapon prefixes
There are also some effects that cannot be found on randomly generated legendary weapons. These are known as unique weapon effects, and that can only be found by adding the effect through commands, or getting the unique weapon that they are found on.