History of Blooming Deep Solo Expert

Blooming Deep Solo Expert is a triumph: complete the Blooming Deep on Expert difficulty without a fireteam. It is a Lost Sector in The Blooming area of The Pale Heart (The Blooming Deep).

How to complete

1. Find the entrance in The Blooming: search the southern edges for a cave entrance marked by the Lost Sector symbol near a ledge with thick vines hanging down; use the vines to guide you and jump up (Prima Games / Escapist summaries).
2. Expect mostly Taken with some Dread; the boss is Azshrunah ur-Nokru the Sacrificed, a Taken Knight. The sector has Champions (Overload and Unstoppable per the in-game text).
3. Launch it alone on Expert (no fireteam). This is the easiest of the three, so use it to learn the layout.
4. Bring weapons effective against Taken and Hive-style shields, and be patient with the platforming.
5. Beware Taken Phalanxes near platform edges; their shield blast can knock you off.

Unconfirmed

Seal and reward were not found in sources I opened, and no exact loadout is confirmed. The linked video shows a solo flawless Master run on Titan.