My theory on the Crown of Thorns is that it is Thorn Manacles for a God or thereabouts
Putting it on their head is another matter.
It would therefore render effectively mortal and powerless any being from a god downwards, so the Faerie Queens, a Naagloshii, the Fae, much of the creatures in the NeverNever etc. It may even have been powerful enough to contain one third of the White God, if so then the Fallen, including Lucifer might be contained by it.
According to Wikipedia the use of a Crown of Thorns was to cause pain and to mock the alleged authority of the wearer, sounds about right.