Xenomorph Tail is an Epic Back Bling in Fortnite: Battle Royale, that can be purchased with the Xenomorph Outfit in the Item Shop for 1,600 V-Bucks or with the Ripley & Xenomorph Bundle for 2,200 V-Bucks. Xenomorph Tail was first released in Chapter 2: Season 5 and is part of the In Space... Set.
Alien Anthology Wiki
