I have no idea. I strive to make my mods to apply their changes to base game as surgically as possible, but its not always as simple. Im currently focusing on other games, mainly BoH.

Is this mod compatible with the ReForged overhaul mod, or any of its sub-mods?

Thanks! :)

Ah, sorry, I apparently had some changes in, but forgot to upload them, the slot addition to the spirit included. Thank you for reporting it.

Found that this mod breaks the Futhark tutor summons added by Walpurgisnacht.
Figured out how to fix it by adding the spirit to the patrons config in the elements folder by copying the fucine tutor.
Like this:
{
"id":"spirit_lanterne_heart",
"slots$prepend":[
{"id":"scholarship","label":"Futhark","actionid":"study","required":{"scholargerman.visible":1,"scholargerman":1},"forbidden":{"scholarrune":1}}
]
}
No idea why this was broken to begin with, but doing this seems to have fixed it. Without this the summoned spirit can be inserted into the study verb but will not be able to do anything. No extra slot for sholarship and a greyed out start button. Walpurgisnacht on its own works just fine. The tutor for old german, Jannings, works fine as well. Other spirits function. Only the Poet of Miracles, Futhark tutor, is broken like that.
Please fix this. I really like both your mod and Walpurgisnacht. :(

The issue with last level skills is that the recipes in base game are removing the skill and creating the new one. That would remove any mutations. I modified the recipes for reason to use xtriggers like the other ones use them, and did the same for passion and health skill cards for consistancy.

Nevermind, seems like an interaction with another mod. Just got suspicious when I saw that this modified the health skill.

I think this is making it impossible to progress health or reason (maybe also passion) to the final level? Haven't quite ablated all the other possible mods (I'll get back to you), but looking at your code it seems like the likely culprit. Also might be good to not modify the health or passion study recipes if you're just targeting the way translation works.