Osiris needs your help with the EDZ Obelisk in Destiny 2. To start unlocking this one, you need to visit him on Mercury and grab the EDZ Obelisk quest called EDZ: Obelisk Attunement.
Step 1: EDZ: Recovery Operation. Once you have the quest, the first step is for you to head over to the planet and collect 50 Cabal Armor Plating. You’ll want to visit the Sunken Isles to find the most Cabal activity. Take out any Cabal you see there, and if you have trouble finding them, check inside of the Echion.
You’ll need to bank those at the EDZ Obelisk when you’re finished, which is right next to The Gulch’s fast travel point.
Step 2: EDZ: Light Collection. Now, you need to collect Light Orbs on the planet. The best way to do this is by killing enemies using your super, your abilities, or a masterwork weapon. After you collect those, similar to the previous step, you need to return them to the Obelisk and deposit them.
Step 3: Timeline Stabilization. Approach the Obelisk, and you will have now attuned it to the Sundial.
Here is the location of the EDZ Obelisk.
If you are experiencing a bug with the Obelisk, we have a solution for you.