Getting the Destiny 2 Captive Cord means you'll have to retrace your steps a bit. It's the Lunar Battlegrounds area in which you'll need to track down this hidden item and craft the Arc Logic auto rifle as part of the Essence of Failure quest.
Like the Destiny 2 Horned Wreath item that gives you a plush new sniper rifle, Captive Cord lets you craft exotic weapons by combining special items with Eris Morn's Lectern of Enchantment, and Nightmare Essence. If you're struggling to find Captive Cord in the Lunar Battlegrounds area, I'm here to help you do just that.
Destiny 2 Captive Cord and Lunar Battlegrounds location
Destiny 2 Ethereal Charms - Essence of Greed
Destiny 2 Necromantic Strand - Essence of Brutality
Destiny 2 Horned Wreath - Essence of Vanity
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Destiny 2 Withered Plumes - Essence of Obscurity
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If, like me, you're not really the observant type, you may not have noticed that you've actually been to the Lunar Battlegrounds before: it's the spot in which you landed to start the Shadowkeep story. Y'know, the bit where you had to fight off waves of baddies before taking in the nightmarish splendor of the Hive-infested Scarlet Keep.
It's this spot to which you must return to get Captive Cord, but it isn't quite clear how to get back there. The best way to start doing that is by warping to the Sorrow's Harbor fast travel point to the northeast. Then head southeast within the Harbor area and you should see the red bridge (and its map location) pictured above.
From there it's a linear route all the way up to where you had to capture the six nodes in the first Shadowkeep level. In case your memory needs refreshing, bear right after crossing the bridge back to your very first landing spot on the Moon.
It's at this point the map marker for the Captive Cord should appear. It's on the building on your right on the second highest platform. Then all that's left is for you to pick it up and start crafting your latest auto rifle. Enjoy!