Now that Drycha is sufficiently dead for our immediate purposes, it's not relevant, but I found this as I was rereading. Might be old news.
The phrasing "rejected by the forest" points away from Halétha, but the debuff largely came from the shadows.
"Halétha intervenes" fits most of the information we have available. Problem is, "Forest intervenes" is a tighter hypothesis- except Halétha's been mucking things up there.
There is definitely at least one spiritual entity. If there are two, they aren't currently at cross purposes, despite LM Kupfer's words. The entity/ies implied in Mathilde's mind that they were the Forest of Shadows, Loren Arhain.
That last sentence is at least partly bullshit, Halétha is pulling a con.
One of the reasons I believe that may just show my Warhammer Lore weakness, but the name. There are lots of place-gods, as we discussed with Kasimir, but the person and the place don't usually have the same names. And when they are similar, it's the place being named after the person. And in Eltharin, on the Imperial/Kislevite border? It's a nice parallel to Athel Loren, but there are no elves (or elf-influenced dryads, lol gottem) here.
Would also explain the entity's motives in firmly opposing Drycha- there's no natural kinship there, this may even be a friend of an (ex-?)enemy.
If there ever was a spirit of the Forest of Shadows, it wasn't just the Shadows that were stolen.