Look at FSC.
It's called Shadow Fire.
I think that there needs to be a weapon which utilizes this fire. I want it captured and harnessed!
(Note: This is a shoutout to all those forum goers who say that there needs-not be a shadow weapon which deals fire. However, I see no reason for this not existing. Actually, I would go as far as to suggest that a miniature version of Vana's mace would drop from Vanaduke as a rare drop. It would work like a Troika but would deal the Fire status and Shadow damage.)
1. 'Shadow' fire deals elemental damage (bye bye your argument)
2. Vana deals normal.
But now that you bring it up, shadow fire should deal shadow damage for the sake of both having a shadow trap and making your suggestion valid.