According to The Verge, a new patch for the game (v8.50 if you're keeping score at home) brings with it a new limited-time event that allows you to either assemble with the heroes — and use trademark weapons from the Avengers — or find yourself playing as the Mad Titan himself.
Unlike last year's event, which tied into Avengers: Infinity War, it's going to take a little more effort to become Thanos. You start out as a Chitauri, and instead of just finding the Infinity Gauntlet, you have to find one of the Infinity Stones to become the big purple curmudgeon. The more stones you gather, the more your powers increase and the more health you bestow upon your teammates. If you die as Thanos, the last player to find a stone respawns as him.
Meanwhile, if you make it onto the Hero team, there's a treasure map that will lead you to a "Mythic Avengers item," each of which is stored in a chest across the map. Among them are Iron Man's repulsors, Captain America's shield, Thor's ax, and Hawkeye’s bow (we're guessing that there aren't any weapons related to the Hulk, unless we're talking about his fists).
The heroes have unlimited respawning capabilities until all the stones have been collected, while the Chitauri have a limited amount. The heroes need to deplete the Chitauri's respawns and kill them before the alien warriors can find all the stones, so players who are Chitauri have to try not to die too often. The Chitauri, of course, want to get their hands on the precious gems and destroy the Avengers.
Fortnite is perhaps as massive these days as the Marvel Cinematic Universe itself, so it makes sense that these two cultural phenomena should collide. And if you aren't familiar with Fortnite, here's where you can catch up.