http://www.pcgamer.com/fortnite-battle-royale-now-has-a-50v50-mode-and-it-looks-ridiculous/

Announced at The Game Awards, a new 50 versus 50 mode is now available to play in Fortnite Battle Royale. The catch is it's only there until December 17. It's leading off a new wave of timed events—timed, likely because making a refined, balanced 50v50 mode would require way more legwork than is worthwhile. Broken, experimental game modes as a temporary diversion from the usual free-for-all are a perfect fit for Fortnite's more playful battle royale arena.

A few minor changes will accompany the mode, including chevrons above all allied players, no splash damage (bummer!), and the ability to revive any down-but-not-out player on your team, even if they're not part of your squad. To get an idea of the kind of chaos 50-player teams on a massive map, armed with bush potions, launch pads, and rideable-rockets can get up to, check out the trailer above. Alternatively, it's not hard to imagine.