Flymm Cargo in BG3 is a building in the northern of Grey Harbor.
Continue reading to learn about Flymm Cargo BG3 and Avenge the Drowned quest.
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Flymm Cargo In BG3
The Flymm Cargo in BG3 is located in the Lower City’s southwest.
The coordinates to the old building are (X:-155; Y:-164).

The building has a basement as well as a few floors. However, the ground-level doors are locked, and people will see you there.
Players can lockpick the balcony door and climb up onto the roofs.
Further, they should kill any appearing enemy creatures.
Avenge The Drowned In Baldur’s Gate 3
It is one of the side quests in Baldur’s Gate 3 which you can accept from a prientress in Wavemother’s Temple.
The temple can be found mourning for the death of Holli.

Moreover, she was a woman who was allegedly killed by a sea monster.
Your task is provided by the priestess to catch Holli’s killer. By doing this, players can pay respect to the Wavemother.
How To Complete Avenge The Drowned Quest?
After accepting the Avenge the Drowned quest, you may see the yellow zone you must search on your map.
The region you need to search is actually underwater.
Further, it is something the game fails to mention.
Also, if you are wondering how to get there, follow these steps:
1. Go To Flymm Cargo
It is located directly west of the Counting House and south of the Blushing Mermaid.
After, you must enter the Flymm Cargo facility which is a building.
2. Lockpick The Door
You should then pick the lock on the building’s front doors and let yourself in.
Then, five wolves will attack you. Make sure to kill them all.
Then, move deeper inside the structure. You should instantly make a perception check.

Further if you succeed, a hatch will become visible in the room’s left-hand corner.
But even if you fail, the hatch is in the front left corner of the area, hidden beneath the crates and barrels.
3. Get To The Basement
You enter the Flymm Cargo basement after going through the hatch.
This is where you must move forward in order to finally find a submarine docking station.
Along with the submarine, Redhammer the Deviser, a dwarf, will be there.

Players should ask Redhammer some questions about what he is doing above the submarine.
He will not deny any allegations and will offer to ride you down the iron throne.
4. Ride To The Iron Throne
Upon reaching the Iron Throne, your primary goal should be saving any hostages and Archduke Ravengard.

Also, players have to make sure to get up the ladder to the sub before the timer runs out.
Moreover, they should also beware of the Sahuagin enemies.
5. Blow Up The Iron Throne
By succeeding, Ulder Ravengard will live, and the Iron Throne prison will be destroyed in the process.
The Wavemother priestess who gave you the Avenge the Drowned quest will await you.
You can again meet her at the Flymm Cargo facility.

Furthermore, she will inquire if you were the one who detonated the Iron Throne.
Saying yes will result in you finishing the quest and earning a very rare chest piece in return.
The Bottom Line
The Flymm Cargo is a transit between the underwater world and land as it has a submarine.
Players can detonate the iron throne by heading towards the basement of the Flymm.