A Company Vanishing Into the Deep is a world quest that you can get and do in The Chasm: Underground Mines. It involves a few Fatui members who have been settling in the mines for an extended period now. This world quest will also hint at the past relationship between the Fatui of Snezhnaya and the Millelith of Liyue Harbor.
To have this quest available for you, you must complete the Surreptitious Seven-Star Seal Sundering quest, which is part of the Chasm Delvers world quest series. Doing so will remove the seal preventing you from entering The Chasm: Underground Mines.
This quest is also needed for you to complete the hidden exploration objective titled ‘Tell a Tale for Teliesin.’
This quest can be started by talking to one of the Fatui in a camp inside the cave in the southeastern part of the Underground Waterway.
You will find 4 Fatui Skirmishers in the camp, an Anemoboxer, a Hydrogunner Legionnaire, a Pyroslinger Bracer, and a Geochanter Bracer.
Starting and Completing the Quest
Step 1: Enter the cave and talk to the Fatui
When you enter the cave where the Fatui camp is located, you will hear someone yell: “You over there, please, don’t attack us!” You can then talk to the Anemoboxer named Anton, the brevet commander of the Fatui’s Ninth Company.
He will introduce himself as the Staff Sergeant Anton Melkinov, the acting CO of the Ninth Company, and then introduce his team. Anton took over as the Staff Sergeant of the company after their Captain went missing. Together with him are Ninth Company soldiers Danila, Temur, Radomir, and Romanski, who sadly did not make it earlier that day.
The Fatui soldiers seem to be arguing with each other because Temur will not accept Anton as the acting Co of the team. Based on their heated discussion, you will find out that the group has run out of rations, is currently not very combat-effective, and is almost losing their sanity.
Anton will ask for your help, and you will be given the option to hear them out or start a fight.
The Acting CO of the Ninth Company will promise to give you anything – supplies, weapons, intel, or Mora – if you help them. They even promised to leave and never return if that’s what you will ask. All they want is for you to give them food.
Anton will also reveal that the only purpose they have in the mines is to investigate the source of the calamity in The Chasm. There were originally 64 of them, but only four remained and are now famished.
In some parts of the conversation where you will be given three options to respond, selecting either of the first two will continue with the conversation. But choosing the option “Ready for combat” will have the Fatui attack you, and you have to defeat them.
Step 2: Give food to the group of Fatui
Your inventory will be opened so you can choose what raw food ingredients or materials you want to give the group.
You can give four batches of Tofu, Unagi Meat, Raw Meat, Fowl, Radish, Tomato, Fish, Rice, Bamboo Shoot, Potato, Carrot, Egg, Apple, or Sunsettia.
Step 3: Defeat the incoming Fatui
As the last members of the Ninth Company are taking their time eating, a group of Fatui Skirmishers will appear. One of them is Corporal Mashkov, Bloated From Hunger, who will be angry at Anton, calling him a traitor and saying that the Acting CO has forgotten what “secrecy” means.
Mashkov and his team will attack you to take your food. Corporal Mashkov is an Electrohammer Vanguard, and the ones with him are a Pyroslinger and a Geochanter Bracers, so make sure to use the right element to break their shield.
Step 4: Talk to Anton
Anton will apologize for having a small issue in their chain of commands, which caused Corporal Mashkov to attack. But Danila will protest because they have betrayed their men by just standing there watching while someone else chased them off.
Radomir will then explain that their chain of command has been wiped out and that their captains and other higher-ranking Cos have either gone missing or killed. This leaves them no other choice but to retreat.
According to Danila, a certain collaboration agreement states that people on the surface are supposed to relay orders and supply them with food, but they have not heard from them for a long time.
Anton will ask another favor from you. He wants you to visit their secret supply station near the ground level this time. It is where all their supplies go through, and sometimes they get orders there, too. After sending a few men up for food with none returning yet, Anton cannot afford to risk another trip. He is hoping you can check the situation there for them.
Step 5: Go to the supply station to look for clues
Fast travel to the Teleport Waypoint in the Ad-Hoc main Tunnel, the uppermost of the Chasm Underground Mines.
When you get there, glide down to the ground level and go to the camp south of the area.
You will find a book labeled a Lost Document on the table in the said camp. Interact with it to read its contents.
“…Emergency Announcement from the Secretary at Yujing Terrace: The malignant and destructive incident recently occurring at the Jade Chamber has proved that the Fatui are dangerous and untrustworthy….”
“…The collaboration agreement with Snezhnaya has been nullified. The Liyue Qixing will take over the exploration of The Chasm…”
“…The Millelith will not make contact with any member of the Fatui. Violation of this will result in immediate arrest without clemency!”
Step 6: Defeat the attacking Treasure Hoarders
After reading the Lost Document, Treasure Hoarders Ratcrow Thief and Rateye Crook will appear talking about a letter from a guy named Yanbo. These bandits will attack, so you have to defeat them.
Step 7: Find Yanbo’s Note and give it to the Fatui
When you defeat Ratcrow Thief and Rateye Crook, you will automatically obtain Yanbo’s Note. It is a somewhat complete note, written in a neat hand, and seems to have been a letter left for an old friend.
Yanbo’s Note reads:
Dear Anton Melnikov,
I’m sorry that the supply station has been shut down due to the sudden turn of events. Our previous plan to drink Fire-Water together upon your return seems impossible now.
I left some food here in secret. It should be enough in the short run. Take as much as you need.
Sorry, as your friend, I can’t do much more than this. Although I am aware that you and your mission have nothing to do with what happened on the ground, please understand that we can never forgive such a blatant act of invasion. The next time we meet, we shall be enemies.
Just as you fight for the Tsaritsa of Snezhnaya, as one of the Millelith, I must protect our homeland. We each have our responsibilities to shoulder for what we cherish.
Best of luck to you. Yours sincerely, Yanbo.
Head back to the cave where Anton and his group are setting camp and tell him the situation at the supply station.
When Anton asks if you find anything, you tell him that the Fatui is no longer welcome in Liyue Harbor and then hand him the letter Yanbo left for him.
After hearing about the situation, the Ninth Company is confused about Millelith’s actions. They know they were fighting as allies with Liyue to protect the Geo nation’s people from the Calamity of the Darkness. Anton will then decide that they need to retreat. The quicker, the better, and preferably in silence without alerting the local Millelith.
Anton will thank you for the help you gave and hand you Mora and some supplies.