Duality is a Tier 1 Paid Track Reward and the Rank 35 Free Track Reward in Destiny 2 Beyond Light.
Anyone who purchases the Season of the Hunt pass will immediately gain the duality, provided they go to the Season tab and redeem the first tier of rewards. They'll also start working on Duality's Catalyst Quest, which requires kills in Strikes, Gambit, or Crucible to "calibrate" it, then a true 50 Guardian kills (yeah) and 100 "Duality Slug" targets defeated (targets killed at using a combination of Duality hip fireballs and ADS slug).
Free players will need to do a bit of homework, but the duality isn't very deep in the Hunting Season Pass in Destiny 2 Beyond Light. If you like to keep your money in your wallet, you can simply reach Season Rank 35, where duality is the free reward. Completing the main story of Beyond Light will get you to rank 8 or so, so you'll want to start taking on additional quests and bounties to increase your rank. There are players who are already cooling off at rank 30 and above, so even casual play can get you to rank 35. You may need to save a few minutes of play every day or two, but it's doable.
The intrinsic trait of duality is the compression chamber, which "shoots a pellet in the fire from the hip or a single high damage slug while aiming." It has Corkscrew Rifling, an alloy magazine and short action stock, but what makes this shotgun singular is the On Black Wings advantage. Pellet kills will grant stacking accuracy and a reload speed buff, and slug kills will extend duration. Reloading drops the buff, but the idea is simple: alternate between shooting from the hip and aiming to maximize the accuracy of the buff, and keep it alive when the time comes for a quick reload.
