Fortnite recently announced its obligatory Halloween event, but its Midas's Revenge mode seems very similar to Call of Duty: Warzone's Zombie Royale. Warzone had released its Halloween event, Haunting of Verdansk, just the day before. With Fortnite's past to "borrow" ideas from other games, it leads to a possibility of Warzone's zombie royale being copied from.
Warzone's Zombie Royale places players in a standard match of battle royale, but the Verdansk map is far more spooky and dark. The event comes with another twist, allowing dead players come back to life as zombies to hunt down their living enemies. Living players also drop syringes on death that zombies can take, two of which syringes allow them to respawn as a human player. Zombies are faster, have special abilities, and can only attack in melee range. This gives an interesting element to the game when played in squads, allowing living teammates to utilize their zombie brethren to hunt down their enemies and help them survive the night.
Fortnite seems to borrow this idea from Warzone with its new game mode, in which players respawn as menacing ghosts rather than zombies. Also, the ghosts are faster, have special abilities, and can only attack in melee range, which all seems familiar. One major difference Zombie Royale provides is zombies' chance at reanimating, whereas death seems more final in Midas's Revenge. While Fortnite and Warzone have enough to differentiate themselves in their standard battle royale modes, both Halloween concepts are basically the same exact game mode with different coats of glow-in-the-dark paint.
There have been times where Fortnite strays from originality and takes other things to use as its own, like when it was pivoted from a lackluster PvE base defense game into a PUBG-inspired battle royale. It notoriously "borrows" dances from the internet to profit off of as emotes, only recently beginning to credit the occasional original choreographer. Apex Legends' pinging system was also "borrowed" by Fortnite in Season 8, being almost an exact copy but with slight changes. While Midas's Revenge may not be an exact replica of Warzone's zombie royale, it is still very possible that Epic Games lifted the idea due to its long history of not being the most creative game on the block.
It's worth noting that Warzone's Zombie Royale was hinted at a while back, as well, meaning Fortnite had plenty of time to adapt the idea and use it as inspiration for Midas's Revenge. To Epic's credit, however, the idea of ghosts (or zombies) coming back to life for revenge isn't exactly unique, so it's certainly a possibility both games had similar ideas at the same time for their respective Halloween events.
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Source: Fortnite, Fortnite/YouTube