- Walk on the platform of teleportation (yellow circle) to unlock them!!!
If you don't walk/interact with them, you don't register them. This is crucial if you forget an item somewhere, to return "quickly" to the region concerned.

- You don't have to do the demons in Zone 1 & Don't die
To finish the game and do all the achievements, you must not die during the run. So you can avoid doing the demons in zone 1. You will do them at the end of the game when you are stronger.
You can play on easy or story, it's the same (it's already annoying enough as it is).
This is not required for item success specifically but might as well kill two birds with one stone.

- You don't have to catch all the species.

- Be careful ! It happens to do a fight right in front of the chest and leave having forgotten to open it

- Stick the walls because the puzzles are sometimes "off" the map and you have to stick the wall to see them.

- Maps with All items location :
https://game-guide.fr/336907-necro-story-guides-des-cartes-et-objets/

- YouTube Video with timelaps for each items :
https://www.youtube.com/watch?v=wphmRpvPw-c

- Another guide :
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3344572333

Items to have Zone 1
Do NOT leave without !
DON'T approach the black gate ! You CANNOT come back !

Staffs
Trinkets 1
Trinkets 2
Trinkets 3
Gems

Items to have Zone 2
Do NOT leave without ! You CANNOT come back !

Staffs
Trinkets 1
Trinkets 2
Trinkets 3
Gems

There are differents parts in Hell.

- 1st part. There is 3 obvious items on the way (one with puzzle).
The last of them is the "Bone Bracelet"

- 2nd part. The next item (4th) is after the First Black Gate. It's a chest after the boss encounter.
The name of the item is "Refreshing Boots"

- 3rd part. The last one, is the trickiest, it's a chest after the "Snake/Dragon" encounter an before the other one. It is "hiden" behind the last Black Gate
Be sure to tape the bottom edge (or the top?) so you don't enter the cave without the chest

If you succeeded, congratulations !
You are part of the small community of players who fought mentally to get it.
It took me 3 runs to achieve (1st run, the discover, the second failed because I got too close to the black door).

I hope this guide helped you. You are probably not far from 100% or you are already there. Have a good time.