Destiny 2's Forsaken DLC introduces a new weekly activity, the Ascendant Challenge. To access it, you must find a rotating location and consume a Tincture of Queensfoil to see the portal entrance to the Ascendant Realm. Queensfoil can drop from a number of sources in the world but if you find yourself in short supply, a skull named Huginn has your back. He will trade you 50 Baryon Boughs, the Dreaming City resource, for one Queensfoil. Here is how to find Huginn.
Go to the Dreaming City. Hook left through a crystal cave at the edge of the map heading back to where you first entered the Dreaming City in the story. Leap over two chasms. At the Spine Of Keres, when you see a tower courtyard, hook left towards a bridge. Stop right at the bridge and look down to your right for a path down the mountain. Follow the path to a portal. Run past the crystal and hook a left at The Confluence. Run past the statue and hook a left at the Harbinger's Seclude to find another portal at the back of the room. This will take you to the room with Huginn. Trade 50 Baryon Bough's and you have a Tincture of Queensfoil, the consumable ticket to each week's Ascendant Challenge.