Dark Vertex is a Legendary Fortnite Outfit from the Dark Apex set.
The Legendary Dark Vertex skin can be obtained by purchasing an Xbox One S - Fortnite Battle Royale Special Edition Bundle. Included in the bundle is the Dark Vertex skin, Dark Forerunner Glider, Dark Razor Pickaxe, and 2,000 V-Bucks. These are a recoloring of the already existing Apex Protocol Set.
Update: You can now obtain this skin by purchasing a Fortnite Xbox One controller!
The bundle with the Dark Vertex skin launched on June 7th, 2019!
Xbox One S 1TB Console - Fortnite Battle Royale Special Edition Bundle Includes:
Gradient purple 1TB Xbox One S console, matching purple Xbox Wireless Controller, download of the free-to-play Fortnite Battle Royale mode, Dark Vertex Cosmetic Set which includes a Legendary Outfit, an Epic Glider, a Rare Pick Axe, 2000 V-bucks, a 1-Month Xbox Game Pass trial, and 1-Month Xbox Live Gold subscription. (Game requires Xbox Live Gold, subscription sold separately. Unlock the Dark Vertex Cosmetic Set in Battle Royale and Creative modes only. Bundle doesn't include access to Save the World mode.)