New Spell: Fog of War

Hello! i have a new idea for a spell.
It's called fog of war and it can freeze 1-2 tower
(s) for XY seconds.
It looks like a dark smog and flies over the tower - maybe this is a reason to pay the spell with DE?
Size shouldn't be bigger than 3x3.

That's it - feedback plz :-).
Regards,
Bärenclan - Co-Leader - Austria

no one like this???

According to some players, the last spell space is reserved for special occasions spells.

Like the christmas special spell! I dunno what it is but I saw it in Wikia