Fortnite: Chapter 2's Season 4 costumes have some entertaining Easter eggs for players to uncover. Mjolnir, Thor's magical hammer, can only be wielded by skins that it deems worthy. The hammer will transform into a boring pickaxe if you hold the hammer as someone else besides Thor or Captain America.
The hammer became a big part of Season 4 after it created a crater in the map last season. Players had to visit the crater while wearing the Thor skin in order to unlock it. Thor's not the only one that can hold it--Captain America deemed himself worthy in both the comic books and franchise of blockbuster movies by picking the hammer up.
According to the description, Mjolnir will be replaced by a regular pickaxe if used by a skin that's unworthy... Here's Captain America wielding Mjolnir. from r/FortNiteBR
Other costumes have special accessories and Easter eggs as well, but they are limited to the specific Season 4 battle pass skins. Some players are disappointed; they wish they could use the special Marvel back blings and pickaxes with any costume.
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