Key items:

These are necessary to finish the game.

Glass Jar

Jar of Liquid

Key

Special items:

These open hidden rooms on the second floor of Building B.

Sheets of Numbers	Mouldy Bread	Old Cigarettes	Blueprints
Букварь	Конфета	New Cigarettes

Standard items:

These do absolutely nothing!

Faceless Matryoshki	Porcelain Figure	Picture of You	Fermented Soda
Sparrow's Skeleton	Icon	Old Batteries	Tarragon Soda
Precious Cup	Worn Penny	Burnt Poem	Old Cola
Canned "Meat"	Cat Cross-Stitch	Paints	Steel Bearings
Onion-in-progress	Honey Cake	Garlic	Someone's Letter

Ending Guide

There are two endings, and both diverge from the final room with the pit.

Happy End

Simply walk towards the ladder in the far left corner of the room, or choose "No" either time when prompted by Nika.

True End

Choose the following choices in the conversation with Nika: Yes -> Either Option -> Yes