History of Barrow-Dyad

Barrow-Dyad is an Exotic Strand Submachine Gun from Episode: Heresy.

Overview

Its intrinsic perk, Panic Response, generates blight as it deals damage. While not firing the blight depletes and the magazine gradually refills; reloading converts stored blight into Blighted Seekers.

Acquisition

Complete the The Taken Path quest, which ends with the Exotic mission Derealize. The first clear drops the weapon (Destinypedia notes guaranteed Deepsight Resonance). Afterwards it can be earned again by running Derealize when it is featured in the Portal. Search snippets suggest you can skip the quest and just run the mission when featured.

Catalyst

There are four catalysts, each adding a perk. Reports say two arrived in Heresy Act 2 and two in Act 3, and the first is tied to an Expert Court of Blades run with the weapon equipped; secret quests (starting with "Dyadic Ascension") are involved. I could not open a page detailing each unlock, so check a guide.

• High-Impact Reserves Refit: rounds at the end of the magazine deal more damage.
• Hatchling Refit: precision final blows or rapid defeats spawn a Threadling.
• One for All Refit: hitting three separate targets increases damage for a moderate duration.
• Target Lock Refit: damage increases the longer the weapon stays on a target.