Here are all collection items in Hellcoming.
School
First floor
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Second floor
11.
12.
13.
14.
15.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Second floor
11.
12.
13.
14.
15.
Sanatorium
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Thanks to Ananasik ❄ for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.