Wizards of the Coast regularly releases limited edition sets of Magic: The Gathering cards with alternate art under the label Secret Lair, the latest of which are, yes, themed around Fortnite Battle Royale.
There are two mini sets, one with five basic land cards given Fortnite makeovers (the Forest is Weeping Woods, for instance), and another with seven reskinned versions of existing Magic cards. Wrath of God, the iconic board-clearing card from white decks, becomes a depiction of Fortnite's circle called Shrinking Storm, while the Battle Bus is a reskinned Smuggler's Copter from the Kaladesh set.
Of all the Magic: The Gathering crossovers, including The Walking Dead, Dungeons & Dragons, and upcoming collabs with Street Fighter, The Lord of the Rings, and Warhammer, this is the one that weirds me out most. Fortnite has already had so many intersections with other media: it's got Batman, Deadpool, Lara Croft, the Ghostbusters, and Hopper from Stranger Things in it. Have they all been backdoored into Magic now? It hurts my head to think about.
I guess both Fortnite and Magic: The Gathering are about battles taking place in extradimensional spaces where the combatants are copies of beings who have been summoned there. Does this mean Jonesy is a planeswalker? What about Peely? I think I need to go have a lie down.
These Fortnite cards are available for a limited time from the Secret Lair website, and come in regular and foil editions. The next crossover in the Universes Beyond series will include cards based on Warhammer 40,000's orks, the current Warhammer fantasy setting Age of Sigmar, and Warhammer football parody Blood Bowl.