Boreas' Frost Blade

You create a blade of ice in your hand. The blade is similar in size and shape to a weapon of your choice, and it lasts for the duration. If you let go of the blade, it shatters harmlessly, but you can evoke it again as a bonus action. As a Magic action, you can make a melee spell attack with the blade. On a hit, the target takes 3d6 Cold damage. Additionally, creatures hit by this blade have their speed reduced by 10 feet until the end of your next turn.