Blizzard

You cause a massive blizzard around you, your allies and you take no damage but for every round an enemy is inside they take 1d10 ice damage. If the enemy is flying when they enter there wings freeze stopping them from flying around.

At higher levels the enemy takes 1d6 ice damage for every spell slot above 2, but ever 4 levels they take 1d10 extra instead, so levels 6,10,14,18 and so on