From Destinypedia, the Destiny wiki
This gun can be obtained by completing the We Found a Rifle Exotic quest. It will start by finding a Khvostov Schematic either by dismantling the old Khvostov, or opening a chest on the Devil Splicers' Ketch in the Plaguelands where Guardians spawn into the game for the very first time using a Splicer Intel Relay, which can be obtained by killing either Brood Mothers or Brood Enforcers in the Plaguelands. The schematic then must turned in to Shiro-4, thus triggering the quest. You will then have to find 3 Khvostov Weapon Parts, each of which can be found in Dock 13, The Divide, and The Blast respectively, followed by Manual Pages, which can be obtained by killing any enemy in the Plaguelands. Once these parts and pages are turned in, the quest then takes the player back to where they were first found on a mission called A Khvostov Rising to retrieve the upgraded Khvostov by killing Kaviss, Splicer Captain.
The Khvostov 7G-0X is a unique Exotic in that it doesn't have an Exotic perk. Instead, its Exotic nature stems from the fact that it is highly customizable; there is simply no wrong way to use this weapon. Although the base stats start off in the middle-of-the road, its potential stems from its modularity.
There are 108 total possible perk combinations available. With this much customization at hand, the player can make this weapon work however they want, making it a very versatile weapon built for all purposes, whether for competing against other players in PVP or clearing out waves of enemies in PVE.
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List of appearances