Among Destiny 2: Forsaken's most notable additions are new subclass branches for every class. That means you potentially get new Supers, adjustments to the way your melee or grenade abilities work, and more. Early on in the campaign, you can easily obtain a Seed of Light--the required item to unlock one of these branches. But obtaining the other two is not quite so easy; the third, in particular, previously required you to hit the Raid. That's no longer the case.
As detailed in the video above, you can now do a weekly bounty from Petra that involves repeatedly completing the Blind Well. Do that, and you'll earn an Offering to the Oracle item. But rather than receiving a standard chest when you turn that item in, as per usual, you'll instead be presented with a portal that takes you to Mara Sov, who rewards you with a special chest that guarantees that sought over third Seed of Light.