In Fortnite, there’s a special segment of quests as part of the “Cold Blooded” event, labeled as “Most Wanted.” Completing these quests will earn you Infamy and grabbing enough of that will net you free cosmetics, like the Gold Blooded Ace skin.
Two of the Most Wanted quests involve the bosses and vault areas. One quest requires you “visit named locations containing Cold Blooded Vaults,” not necessarily requiring you to open them up. Another quest requires you to “collect a Vault Keycard dropped by a defeated Cold Blooded Boss.”
There’s a boss and vault in Shattered Slabs, Brustal Bastion, and Faulty Splits. Luckily, in each of the three areas, the boss drops the keycard and the boss is also pretty much directly outside of the vault, making it easy to figure out. You’ll run into some small-fry NPCs around the boss, but you’ll know you’re fighting the boss: Their health bar will have a blue shield (as boss NPCs usually do).
The best thing to do is to drop in the area, gear up with some weapons and shields, take out the other players, and then head to the vault area. If you go there and see that the boss is gone and the vault is already opened, that means another player must have gotten there first.
Once you take down the boss, you’ll need to pick up the Vault Keycard, which takes up an inventory slot. With the keycard selected, an arrow will point you towards the vault.
Inside the vaults, there’s tons of loot, like gold bars and Boom Sniper Rifles, which should help you complete other “Most Wanted” quests as well.
New “Most Wanted” quests will drop weekly, and you won’t be able to get the Gold Blooded Ace skin for around four weeks. There are five weeks of quests, so you likely won’t need to complete every “Most Wanted” quest to get the skin.