Skif in S.T.A.L.K.E.R. 2: Heart of Chornobyl managed to reach Zalesye, but no one will help him just like that. It's time to settle in the Zone and make new useful acquaintances.
Exit the bar, and a stalker will immediately call you over. Talk to him to get the coordinates of the local trader and technician. Visiting them is a side quest, but these are useful acquaintances, so complete the quest immediately, following the markers. Go to Bata.
In the house, you will meet Richter. He and Bata are discussing Kosoy, whom Zotov was looking for. Talk to them and take the task.
You can go to Zotov. He needs sensors that Kosoy stole. It is better to eliminate Kosoy himself. Thus, you will have two mutually exclusive options for the development of events, which one to choose is up to you. The quest will pause, and you will start the task Needle in a Haystack. After its completion, the main storyline will continue.
After solving the problem with Kosoy, Richter will tell you about a certain Sphere — a base where, according to rumors, important scientific research is being conducted, and a map of the Zone is being drawn. Prypoy works for one of the people involved with the Sphere. You need to infiltrate the abandoned communication hub.
When you reach the place, you will see a large sphere with a huge number of gravitational anomalies inside. Here you can find a artifact. You need to get into the basement passage, but to do this, you will have to enter the sphere itself.
Using the old key that Richter gave you, open the nearest door. You will enter an abandoned bunker. Move forward along the only path until you notice something hovering in the air. This is a phantom anomaly that will constantly deal damage. It's better not to waste bullets on it, but quickly inspect all the bodies to find the necessary information. Once you pick up the audio recording, return. You have learned the entry password to the Sphere.
Now you need to infiltrate the main base. This is a large area with many aggressive soldiers, so it is advisable to prepare.
We got underground through the main building on the base's territory, there may be another way. Clear the floors, and when you find yourself in the hall of the main building (the entrance is marked with an English abbreviation), find the descent to the basement. You will still face soldiers, but there is only one path, so you won't get lost. At a certain point, a cutscene will start and Skif will find Prypoy. After the dialogue and battle, choose to kill him or let him go.
As soon as you make a decision, soldiers will rush in. Fight them off and go through the corridors until you see murky water. Descend directly into it and crawl through the low tunnel. Mutant rats will appear. This is a whole horde of aggressive animals, so you will have to fight them off. Clear the area and exit. You will find yourself in a spacious room, but you will have to go through the next tunnel again.
Once out, go to the staircase in the far left corner. You will emerge into a corridor with acidic anomalies. Try to get through them quickly, after which Richter will contact Skif and tell him how to get the key to the checkpoint to enter the main area of the Zone.