Boreas’s Breath

You freeze standing water in a 20-foot cube or running water in a 10-foot cube centered on you. The water turns to solid ice. The surface becomes difficult terrain, and any creature that ends its turn on the ice must make a successful DC 10 Dexterity saving throw or fall prone.

Creatures that are partially submerged in the water when it freezes become restrained. While restrained in this way, a creature takes 1d6 cold damage at the end of its turn. It can break free by using an action to make a successful Strength check against your spell save DC.

Creatures that are fully submerged in the water when it freezes become incapacitated and cannot breathe. While incapacitated in this way, a creature takes 2d6 cold damage at the end of its turn. A trapped creature makes a DC 20 Strength saving throw after taking this damage at the end of its turn, breaking free from the ice on a success.

The ice has AC 10 and 15 hit points. It is vulnerable to fire damage, has resistance to nonmagical slashing and piercing damage, and is immune to cold, necrotic, poison, psychic, and thunder damage.