History of Bloomed Overthrow

Bloomed Overthrow is a triumph for Overthrow in the Pale Heart: progress through Overthrow levels 2 and 3 and loot the chests. Overthrowing The Blooming grants additional progress. The bar is 100 progress.

How to complete

1. Finish the The Final Shape campaign; Overthrow unlocks afterward (TheGamer).
2. Go to The Blooming, start Overthrow there, and work through its levels. The first three levels are public events and encounters, the last is a boss (TheGamer). Public events give about 500 progress toward the goal (Shacknews).
3. Loot the Overthrow chests at levels 2 and 3, since the triumph says to loot them.
4. Completing the whole zone (the boss) in The Blooming gives extra triumph progress.
5. Overthrow progress resets when you leave the Pale Heart, so stay in the destination and finish the run (TheGamer).

Unconfirmed

Seal and reward not found in opened sources. A Steam thread titled "pale heart triumph to kill overthrow bosses will not complete" suggests some Overthrow triumphs have bugged; I did not open it.