I was replaying the game and noticed how this and Spiralhorn are identical in picture
The guilty, the exiled, the penal forces, the thorn sorcerers, the Fire Giants and the Spirit Tree Avatars were all connected to the Golden Crucible. The Staff of the Guilty also shows that thorns are created by blood saplings similar to those found in battlefields and mass graves.

This woman is the Formless Mother, a Crucible maiden that had her eyes removed and thorns grew fron the wounds. The shield is similar to the Ascenstral Spiralhorn shield and this effect manifests ever since the Golden Crucible was turned into the Scadutree.
This is why Stormveil, which has an ancient burial side undernearth, is growing thorns and the soldier€ there are covered in them (which clearly doesn't come from their body and is also eroding their armor as much as the Castle Walls).

The Golden Order/Erdtree faction only later adapted is as symbol of Sin and Punishment, which is why the Bell Bearing Hunter was covered in iron to resemble thorns and prisoners were given outfits that imitate thorns.

The Purebloods seek cursed blood in defiance of their connection to the Erdtree, and it's very likely the sanguine nobles are result of mutationsm. In order for a Tarnished to be initiated as Bloody Finger, he must have the blood of his maiden imbibed in the nail. That's the communion with the Formless Mother