While the Eldrazi hit various Lovecraftian
concepts in terms of the creatures' appearance,
Shadows over Innistrad seems to
be doing the
other element of the Cthulhu Mythos: the fear of
cults and aberrant worship, of dark mysteries
and things that should not be known by mortal
men. To me, this was always the more important
side of the Mythos, and the scenario depicted on
this card could fit in any number of stories. In
Magic terms, this is an interesting sort of
card, giving you a solid defensive card at the
stages of the game you most need one, and
possessing the potential to turn into a
game-ending creature at the time you most need
that. I would try it out in Delver-style decks
as a defensive card against Zoo and an
aggressive card against control (when combined
with the trademark cantrips, and it seems like
that's not even the only major application for
it.
A cheap blue creature that starts out as a
simple Wall, but as you cast instants and
sorceries, it slowly threatens to break free
into the kind of nasty leviathan Blue is always
threatening to summon, but can never seem to do
so without jumping through all sorts of hoops.
Compared to things like Island-Fish Jasconius or
Kederekt Leviathan, I'd say this is a pretty
good deal. A Blue deck that wants to get a huge
creature like that out is a control deck, as it
needs to survive until the late game. Control
decks like having instants and sorceries to lock
down the opponent with, and also like having
cheap creatures that block effectively and
prevent the opponent from dominating the board.
Thing in the Ice is a cheap blocker, and it
transforms as a result of you playing instants
and sorceries, so even untransformed it's a card
you'd probably play and it rewards you for doing
things you'd do anyway.
Alternatively, you could attempt a
"turbo-Horror" deck that seeks to drop this and
then string together a quick succession of cheap
spells to "ramp" your way to a 7/8 and a
board-wide bounce even earlier than a Green ramp
deck could hope to hardcast such a thing. Time
will tell if the pieces are there to make it
happen.