Blue-Flame Blade

You evoke a blade of deceptively cold flames within range that lasts for the duration or until you cast this spell again. When you cast the spell, you can make a melee spell attack against a creature within 5ft of the weapon. On a hit, the target takes cold damage equal to 2d6+your spellcasting modifier. A target hit by the attack has its speed reduced by half until the start of your next turn, as frost begins to wrap across its body and slow its movement. If a critical hit is scored with the attack made with the blade, the target is instead petrified until the start of your next turn after it takes the damage from the attack. 

As a bonus action on your turn, you can move the weapon up to 20 feet and repeat the attack against a creature within 5ft of it. 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 2d6 for every two slot levels above 4th.