After avoiding all the dangers while exploring the "Hadal Blacksite", you've reached the halfway mark, which is located in the room 50. Until you hear the unknown voice inside the vent, then you've decided to crawl inside of curious. Then you find out Sebastian Solace, the shopkeeper.

Sebastian: Hello, nice to meet you. You know the drill, ill offer you those items that are attached on my pouches, but in exchange ill take your reasearch datas that you've been gathering. Deal?