History of Broken Deep Solo Mastery

The The Broken Deep is a Lost Sector in The Impasse on the The Pale Heart, added with Destiny 2: The Final Shape. Reaching it: from the Impasse spawn, open the map and head south toward the Lost Sector icon, hop across the marked pillars, then follow the path past rusted vehicle skeletons upward; the entrance is on your right (per the Escapist guide).

This triumph requires completing the sector on Master difficulty without a fireteam (it need not be flawless; see Broken Deep Flawless Solo Mastery for the no-death version).

How to complete

• Master setup (per a Destiny Tracker listing, not opened in full): Overload and Unstoppable Champions, Arc and Solar shields, Strand threat, Dread and Taken enemies, with Locked Equipment and Extra Shields as modifiers. Bring Overload and Unstoppable anti-Champion mods and weapons matching the shield elements.
• The sector is described as full of tight rooms and platforming (Escapist), so mob management in confined spaces matters.
• The end boss is a Dread miniboss that periodically shields itself. Destroy the floating splinters scattered around the arena to break the shield and open a damage window (Escapist, Destiny2Focus).
• Creator videos show solo Master clears on Prismatic Hunter (Microcosm), Prismatic Titan and an "invincible" Titan build; they are listed in the sources, but only their titles could be read, so builds are not detailed here.
• Master completions reward weapons at a 100% rate with an extra perk in the third or fourth column (Destiny Tracker listing).

It is worth 5 points. Its seal and any reward are unconfirmed from the pages opened.