I think this suits death well. I think a name change may help pitch the idea better though, maybe something like absorb soul rather than revert (tends to give the impression you would get quanta instead). Name change or not though it would be a strong card for death.
The upped version may be a bit too strong though, either up its cost by 1 to 2 or keep the same effect as ununpped but make the card cheaper. I wonder if making it the cost elementless would make it to OP since it ultimately asks to sac a creature? Anyone have an idea?