The Leviathan’s Breath has finally received a catalyst, a catalyst that gives it increased ammo. This helps with the overall damage of the weapon since you are able to shoot more arrows.
It is relatively easy to find the catalyst, you need to kill powerful enemies with Leviathan’s breath. That sounds painful, but all you need to do is head on over to the Widow’s Walk Lost Sector in Trostland on EDZ.
In this lost sector you kill the two Nightmare shanks, then the Lost Sector Boss, after you kill the boss two more shanks spawn. When killing the Lost Sector Boss you definitely want to weaken him a bit before shooting him with the Leviathan’s breath so that you can save ammo. If you run out of ammo, all you need to do is head over to a public event flag and get your 10 shots, 12 with double reserves.
After you get the catalyst, you can either get 1500 kills with the weapon, which would be a pain in the ass, or you can use the Cryptolith Lure to advance it by 15% each run. One of the options in your Cryptolith Lure is Leviathan’s Breath Catalyst Progression. When you choose this option, you don’t even have to run the weapon to get progress on the catalyst. The only downside is that you don’t always have the option to get bonus catalyst progression, and you have to charge your lure 3x after every 3 runs, or 1x after every run, depending on how you want to farm it.