As if Fortnite Battle Royale smashing a comet into the map and wiping out an area wasn't fancy enough, it turns out that comet contained the Infinity Gauntlet from those there Marvel movies. A new solo event mode lets one player grab the Gauntlet and be transformed into Thanos himself (the chinny smurf from Avengers: Infinity War), wielding superpowers as other players try to take 'em down and have their go with the glove. It adds an interesting element of uneasy and fleeting alliances, as Thanos is too tough for any one player to kill alone but everyone ultimately wants the win themselves.
So, yes, the comet has brought an Infinity Gauntlet to the land of Fortnite. It just has, okay. It spawns somewhere on the map soon after a round starts, and whoever grabs it gets transformed into Thanos. He doesn't use guns and can't build, but he sure can fight.
The Gauntlet left-clicks for a mighty punch, holds right-click to blast a beam, and lets Thanos charge up a big jump that launches him into the sky, where he can hang out beamblasting or slam down with a big area-of-effect thump. He's a beefy boy, starting with 300 shields (which regenerate with kills) and 700 (non-regenerating) health. Everyone else is pretty tough too, mind, as the mode only spawns Rare, Epic, and Legendary-quality weapons, and you get more building materials and ammo too.
When the Thanos player dies, the Gauntlet sits around for a while, waiting for someone else to snatch it. Slip it on and you'll rocket into the sky then get to drop back down for your own rampage. I have seen some good fights with players using the Gauntlet as bait, picking off people as they charge for it - loot more valuable than any crate drop.
I have enjoyed seeing Thanos fight in urban areas, leaping up above the rooftops then smashing down through a building all the way to the ground, demolishing walls with a swipe of his fist. He really makes areas look like they've hosted a superpowered rumble.
As cross-brand marketing events go, it's neat! Very fancy. I am half-surprised it's taken so long for Epic to #leverage their #brand with promos, but I am glad they saved it for something neat rather than e.g. slapping in Dorito-shaped gliders and Mountain Dew shield potions.
The Infinity Gauntlet event mode won't be around forever. If you fancy a go, Fortnite Battle Royale is free to play through Epic's client.
See the version 4.1 patch notes for more on Infinity Gauntlet and other changes in the update. Final circles are now 25% more likely to be near the edges of the map, for starters.