[Autumn]

umm you didn't buff dark cinders, you've quintupled the cost, and the only thing changed is you can convert tile at a cost of 2 per tile.....

that would make it even less desired.

I would personally leave it 1 void per tile,  and make the cinders scale on 75% of your dark +75% of your fire attack.

You seem to have drastically misunderstood the suggestion. Right now, if you use blazing crystal rose, as an example, it takes 9 void energy. Under this suggestion, it would take 5, and presumably be subject to the half-cost passive VA has.

Void Reverb unfortunately only can work on void energy costs more than 2 atm. The benefit of dark cinders is they're not affected by enchants like firewalk but the benefits are not very worthwhile of a void energy cost.

For this reason I think Charred void doesn't need to cost void energy at all, OR it needs to increase the cinder's level by an additional 25% of your Dark ATK.