As an action, make a weapon attack.
On a hit, add 2d8 + your spellcasting ability cold damage to the attack’s damage roll and the creature must succeed on a Fortitude saving throw or either it has disadvantage on weapon attack rolls or it is slowed 1 for the duration.
On a critical hit, add twice as much damage.
On a miss by 4 or less, add half as much damage.
The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
You can increase the damage by 3d8 for each additional mana expended.