Cryovain's Wrath

You conjure an ethereal white dragon and direct it to bite one creature you can see within range. Make a melee spell attack against the creature. On a hit the creature takes 4d12 + your spellcasting ability modifier of piercing damage, and an additional 2d12 cold damage. If the target is Large or smaller, it is grappled (DC 10 + spellcasting modifier) until the end of your next turn by the ethereal dragon. While grappled, it is restrained.  At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the Cold damage increases by 1d12 for each slot level above 3rd.

At level 8, you can channel the fear caused the ethereal dragon to stop enemies in their tracks as a bonus action.

Draconic Fury: Each creature of the dragon's choice that is within 120 ft. of the Dragon and aware of it must succeed on a DC 14 Wisdom saving throw or become Frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

At level 10, you gain control over the ethereal dragon and can force it to unleash a breath attack on a bonus action. 

Cold Breath (Recharge 5-6): The Dragon exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 15 Constitution saving throw, taking 45 (10d8) cold damage on a failed save, or half as much damage on a successful one.

At level 15, you gain mastery over the ethereal dragon and can call Cryovain on both hands allowing you to use both hands as attacks.