This card has a very strong ability in the
abstract, but it's not the sort of place that
constructed Magic always goes. A deck with a lot
of sorcery and instant spells is likely to make
some of them be things that get creatures off
the table entirely, in a less situational
manner. While it does add value to spells that
don't have effects like that in the first place,
and effectively double up on tempo plays like
Unsummon, that may not be enough to go in every
spell-based or even prowess-based deck. It makes
up for it somewhat by being very strong in
limited, and there may be a niche for it in a
theme deck based around flashback or the like,
where it can be engineered to
effectively clear a table for very little mana.
Nibilis of Frost is a very blue creature, if
nothing else. It flies, and it rewards you for
casting instants and sorceries, which is
something blue likes to do. "Freezing" blockers
or potential attackers is also a very powerful
effect. It's even fairly costed, and 3 toughness
can push it out of burn damage range after a
single spell.
I think this card definitely can find homes in
spellslinger-type decks, the decks packed to the
gills with instants and sorceries meant to
inflict large amounts of damage and punishment
to the opponent. And even if you don't draw into
them, he can still beat face as a 3/3, which is
hardly the worst thing in the world. His
efficacy in Limited is lessened because of its
tendency to want a lot more creatures in decks,
but the body on its own should be sufficient.
