In all fairness (memes aside), I do think we’re taking things a bit too literally.
If people’s desires created the devil fruits, its likely that their fears do as well. And devil fruits come from futures that people envision, whether thats for better or worse.
For example:
An island like Drum may fear a future where the cold will grow too harsh to handle - Hie Hie No Mi
or
People living in darkness and destitution may dream of a future in the light - Pika Pika no Mi
The treasure on Mariejoa may be a “totem” that collects these feelings and creates devil fruits out of them (A devil fruit tree) and that’s why they have so many powerful fruits at their disposal.
This also might be why the Yami was labelled as the most evil fruit too. I think Sengoku said it? Or Shanks or someone else?
Tbh, thinking of Tot Musica, the Demon King itself, given how that came to exist in OP and how it weaponised itself, it feels like a deliberate "foreshadowing"/tease/allusion by Oda in regards to the history of DFs especially the Yami one too.
I haven't played Okami in years (but will replay it soon and complete it too) but i remember the final villain was called Yami too, a sentient ball of darkness and a demon/evil god or something?
It was the manifestation of evil naturally, but fear, hate, despair, greed etc I think? From everything in the world unified into it?
I might be wrong about this but it would make sense if the Yami DF had this too.
I actually expected it to have various souls trapped in it and BB might hear then screaming/agonising in his mind due to it?
Concepts like that always really fascinate but terrify me too lol.
I love your idea about the totem there too! Very creative and dope!