Behelit

This pretty bauble finds itself in hands of your party.

How is it used and who uses it?

No one.

Our party is hopeful and generally good people.

My sorceress who is actually a strange "metaphysical atrocity" uses it as a paperweight

It's been a long time since I watched berserk, what it do?

Opens the gate which bridges the astral world with the material one.
You sacrifice something (mostly someone) dear to you and in return become an apostle. Basically a powerful demon.
The one in the picture is a crimson behelit though, it's a bit stronger. All behelits are predestined. If
one was fated for you it will always find you. If it wasn't you will lose it or it will be taken from you.
Even 39 volumes later it's not clear why they exist and what's the end game really

>Hopeful.
There you go, when your hopes come crashing down, when you are at your lowest point. Ole' bechie is there for you.

Kids who get into berserk will be finishing the last chapter when they turn 60.

DtD.

My character uses it, becomes the strongest Chosen of Tzeentch.

...I'm pretty sure that he's obliged to try to use it.

Seeing as I basically have dropped a lemarchand box in the lap of my players this is pretty much what is happening right now, since berserk has been heavily influenced by hellraiser.
Shit's cool, though they are extremely weary after a scholar who was tasked with finding out more about the box has killed himself and now most of them want to throw it into a volcano.

Each one is tied by destiny to a specific person so much so that even if they lose it or have it stolen it will always return to their possession.

At the lowest point in the persons life, where all hope is gone and the owner enters true despair the facial features of the behelit will align into a proper face and scream.

This summons a collection of demi-gods/demons and they offer a choice. Power and immortality but at a severe price.

Their price is the sacrifice of those most important to the owner of the bauble. This price must be paid willingly, not compelled magically.

This power and immortality allows them to turn into demonic beasts called Apostles but their human forms all have some kind of beastly countenance.

Most behelits are gray, green or yellow. The Crimson Behelit only appears to certain people, those destined by Fate to become the next member of the collection of Demi-Gods that oversee the creation of new Apostles, the Godhand.

Each person that has used a Crimson Behelit has been seen and implied to have sacrificed large amounts of people, from an army of several hundred men to possibly an entire kingdoms worth.

The antagonist of Berserk, Griffith, sacrificed his entire army of blindly loyal soldiers to fuel his transformation into the Godhand Femto after he had been tortured for weeks, all his tendons cut with his tongue and genitals removed.

With his new demonic form regenerated he then made his best friend, the series protagonist Guts, watch him rape Gut's girlfriend(?) and his former second in command, Casca. Casca was pregnant with Guts child at that point and this caused her to go soft in the head and miscarry but the fetus "survived". Then through a convoluted series of events involving an Apostle shaped like a Behelit eats the ghostly fetus mutant that had protected his mother for years from demons and evil spirits, becomes the body for a resurrected Griffith into the real world