To my knowledge, this is the first
representation of a vampire transforming into
mist in Magic. That seems to be a less
compelling element of vampire mythology than
others;
it's rarely used in other settings as
well. For example, Buffy the Vampire Slayer
seemed to feel that it was an ability unique to
Dracula (who they also misused and underused,
but that's a story for another time and place).
There's little your opponents will be able to do
to stop this creature in combat. Something like
Rebuke won't even work as long as you have mana
up, though it will prevent the damage if they
wait until after you used its unblocked trigger
and flipped back (forcing you to flip again). I
assume things like this are why the main Wrath
of God variant in this set exiles, which may
turn some people off this creature, making it
odd design - but that's a story for another
time. Not me, though. I think this is a good way
to make a creature that "only" attacks and
blocks be relevant and raise questions of
opponents.
A neat combat trick for an unblockable 4/4 hit,
though it's really expensive. sure, it enables
madness, the idea of an unblockable hit is
intriguing, but there's menace, and that can be
effectively unblockable. there's deathtouch.
hell, the original unblockable, flying. there's
so many other, better options, I can't recommend
this. Flavorwise, it's neat, I like the design,
but the overall playability is tantamount to a 0
across the board.