Avenge the Drowned is a side quest in Baldur’s Gate 3 that you accept from a priestess in the Wavemother’s Temple in the Lower City. The temple is in mourning for a woman named Holli, who was killed by an apparent sea monster. The priestess charges you with finding Holli’s killer so you can honor the Wavemother.
When you begin this quest, you are not given much information whatsoever. All you know is that you need to search for Holli’s killer in a large area near the docks in the Lower City. If you are struggling to complete, or even progress, this quest, then fear not — I will show you exactly what I did.
Completing Avenge the Drowned in Baldur’s Gate 3
If you look on your map after accepting the Avenge the Drowned quest, you will see the large yellow zone that you need to search. What the game doesn’t tell you, though, is that the area you need to search is actually underwater. How do you get there, you might ask? You will need to head into the Flymm Cargo building directly west of the Counting House and south of the Blushing Mermaid.
You need to lockpick the front doors of this building and once you do and open the doors, you will be attacked by five wolves. Kill them and then proceed further into the building. You should immediately roll a perception check, which reveals a hatch in the left corner of the room if you pass. Even if you don’t pass, though, you can find the hatch underneath the crates and barrels in the front left corner of the room.
Going down the hatch places you inside the Flymm Cargo basement, which you need to progress through to eventually find an underwater docking station for a submarine. The submarine will be present along with a dwarf named Redhammer the Deviser. Talk to Redhammer above the submarine and ask some questions about what he’s doing there. You can also mention how you know the submarine killed Holli, as it’s the sea monster the Wavemother members mentioned.
Redhammer will not deny any allegations, and will even offer to take you down into the Iron Throne after you pass a check. The Iron Throne is an underwater prison that houses family members of those working in Enver Gortash’s Steel Watch Foundry. Traveling to the Iron Throne will cause Gortash to call you via a hologram and say that if you progress to the Iron Throne, he will blow it up.
If you want to complete Avenge the Drowned, as well as find Duke Ulder Ravengard for the Blade of Frontiers questline, then you need to head forward anyway. Upon reaching the Iron Throne, your primary goal should be saving any hostages and Archduke Ravengard.
You only have a set number of turns to do this, though, so I recommend splitting up your party in different directions to save as many people as possible. You just have to make sure you get up the ladder to the sub before your timer runs out and watch out for the Sahuagin enemies.
Succeeding will keep Ulder Ravengard alive and blow up the Iron Throne prison in the process. I found it nearly impossible to save every hostage, though. When the sub returns to the Flymm Cargo building, you will be greeted by the Wavemother priestess who gave you the Avenge the Drowned quest. She will ask if you were the one who blew up the Iron Throne, and saying yes will result in you completing the quest and receiving a very rare chest piece in exchange.
Avenge the Drowned is now complete in Baldur’s Gate 3.