A new item has actually gotten here inFortnite Fireflies and the Firefly Jars are both available in the game if you know where tolook The main way to find Fireflies is to keep your eyes open while you run around the map and play thegame Fireflies can randomly spawn near trees and campfires, and you should be able to area them as they will give off a soft warm radiance on the surrounding area.
When you find them, run up and engage with them and you will get them out of the air and create a Firefly Container. You can throw the Firefly Jars at enemies or structures. If you hit another player with them it will do 40 damage, and then continue to do tick damage to them if they remain in the flames.
If you throw them at a structure then the structure will catch fire and will take 10 tick damage every second up until the fire burnsout With a little screening, it appears that enemy structures will just remain burning up until they are gone, and the fire can spread out in between various build panels. This makes it an intriguing late-game item, as you can add some awkwardness to events by tossing Firefly Jars at enemy constructs and strip them of cover that way.
You can bring up to the 3 Firefly Jars at a time, and will not be able to harvest any more Fireflies as long as you have a full stack.