Destiny 2 brings the new Undercurrent weapon, an alternative to the legendary Forbearence for detail farming without the need for raiding.

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If you were to create a list of the best weapons in Destiny history, there's no doubt that the Forbearence, a Wave Frame Chain Reaction Grenade Launcher from Vow of the Disciple, would be high on it. It's easily one of the best war-cleaning weapons in the game, if not the best, and many people have been using it consistently for years, racking up thousands of kills.
However, it's a raid weapon. And a huge portion of the Destiny community doesn't raid. So now, Bungie has finally found an alternative that players can farm, placing it in regular Nightfalls and GM Nightfalls starting this week.
This new Destiny 2 weapon is the Undercurrent, also a Wave Frame Grenade Launcher. However, it differs from the Forbearence in that its main attraction isn't the chain reaction, but rather the Voltshot, which detonates targets after a reload, spreading chains of fire to clear areas.

So, what is the ideal roll (combination of traits) for Undercurrent?
- Lead from Gold/Voltshot for more frequent pellet delivery.
- Ambitious Assassin/Voltshot to reflect Forbearance's ideal roll a little more.
- Demolitionist/Voltshot for instant grenade recharge and lots of energy benefits after clearing enemies.
There's some debate about whether Forbearence is simply empirically better than chain reaction because it doesn't require reloading after a kill to activate. I'd agree with that, although there's something to be said for the jolt keyword interacting with other elements of an arc build in a way that chain reaction doesn't.
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Undercurrent is also the GM weapon of the week in Destiny 2, so you can get an adept version of it, similar to how Forbearence also has one. While you don't raid, I'm not 100% sure if you GM, so you can definitely farm lower tiers to get a regular one and try to get god rolls that way. 1 in 6 chance of getting Voltshot. Also, it's a week of double Nightfall rewards plus the arrival of this new, really cool weapon, so if there was ever a week you wanted to farm it, this is it.”
Source: forbes.com
