A high-ranking Fortnite NPC, known as Rook, is preparing ground troops for the fall of the Mothership. To gain a tactical advantage, she wants loopers across the island to upgrade their weapons. Although the IO does have powerful weapons, there's nothing like shooting aliens with a customized Legendary weapon. With that being said, players who agree to upgrade their weapons will receive 30,000 experience points as a reward."Upgrade to an Epic or Legendary weapon" Week 13 Epic Challenge (Image via Lazyleaks_)Note: Fortnite Week 13 Epic Challenges will go live on September 2 at 10.00 am Eastern Time.How to complete the "Upgrade to an Epic or Legendary weapon" Week 13 Epic ChallengeIn order to complete this challenge, players need to locate an upgrade bench and upgrade any weapon to either Epic or Legendary tiers. Crafting weapons using Nanites will more than likely not work.In order to craft and upgrade weapons in Fortnite, players will need some gold bars. Although they aren't that difficult to come by (as players can find them simply by looting chests), a lot of them will be needed.Oh yea upgrade benches are back #Fortnite pic.twitter.com/PSCHrcj6OM— #LG Vanity (@ExiIedVanity) June 8, 2021How to collect gold bars fast in Fortnite Season 7An easy way to get gold bars in-game is by completing timed challenges which can be obtained from payphones or by eliminating players marked for elimination on the bounty board.Depending on the individual skill level and proficiency in Fortnite, the time taken to get the needed amount of gold bars may vary. However, for the average player, two to three matches will be needed at the very least.How to upgrade a weapon to Epic or Legendary tierIn order to upgrade a "Rare" weapon using an upgrade bench, players will need 400 gold. It will cost 500 gold to upgrade from "Epic" to "Legendary." Keep in mind that the weapon only has to be upgraded once in order to complete the challenge. There are a total of 18 upgrade benches located on the island. Here are their locations:Lonely LanderCatty CornerRetail RowDirty DocksCompact CarsCorny ComplexSteamy StacksCraggy CliffsSheriff's OfficeDusted DepotRisky ReelsHydro 16Shanty TownThe Durr BurgerViking VesselBeliever BeachCrashed CargoSouthwest of Lockie's LighthouseReaders can watch this video for more information:Also Read: Fortnite Chapter 2 Season 7 live event leaked: Start date, countdown, Misty Meadows destruction, and more revealed