Cryomancy Magic

Specializing on ice magic, wizards that have learned from the Cryomancy arcane tradition manipulate the crystalline structure of ice and bend it to their will. Many foolishly only see this magic as beautiful, and it is, but within the beauty of all that shimmering ice, is a slow and shivering death.

Frigid Magic

Your manipulation of ice allow you to acclimate to it and change the properties of spells. When you cast a spell that deals damage, you are able to change the damage type to cold damage unless its bludgeoning, piercing, or slashing damage. You can use this feature a number of times equal to your Intelligence modifier (a minimum of once). You regain all expended uses when you finish a long rest.

You gain resistance to cold damage. When you reach 13th level on this class, you also gain resistance to fire damage, and at 17th level, you gain immunity to cold damage and the area 5 feet of you has the effects of extreme cold.

Ice Sculpting

As an action, you can freeze a 5-foot cube of nonmagical water. The cube will remain frozen for one minute or until your concentration ends (as if you were concentrating on a spell). You can manipulate the ice as a bonus action to mold its shape to form objects or structures. The objects or structures you make have hit points equal to your wizard level. At 8th and 15th level, you freeze an area of 15-foot and 25-foot cube respectively. You can also create the ice out of moisture in the air, though the cubic footage you are able to manipulate is halved (i.e. you can produce a 7-foot cube from a 15-foot cube of air).

Additionally, when you reach 15th level you can also freeze magical water, manipulate magical ice, and the cube can now be frozen for up to 1 hour.

Cryostasis

Your body fills with ice magic and acts at times in preservation from external factors. When you become unconscious or asleep or are rendered unconscious or asleep, you are immediately encased in a layer of dense ice. This ice has hit points equal to twice your wizard level and an AC equal to your spell save DC.

When the ice encases you as a result of being reduced to 0 hit points, the ice will stabilize you and freezes the area around you. All creatures within 10 feet of you must make a Constitution saving throw against your spell save DC or be restrained until the end of their next turn. On a successful save, they are not restrained but their speed is halved. When the restrained condition from this feature ends, the creature's speed is also halved. They can make another Constitution saving throw at the end of each of their turns. On a success, their speed returns to normal.

The ice lasts for 1 minute, until it is destroyed, or when you choose to break the ice upon regaining consciousness. Once this feature is used it cannot be used again until a long rest.

Absolute Zero

Your control over ice have reached to an abnormal extreme, even by magical standards. Choose one wizard spell that deals damage in your spellbook. That spell's damage type permanently becomes cold damage when you cast it without using your Frigid Magic feature or other similar effect. You can change the spell for a different spell by spending 8 hours in study.

When you deal damage to a creature that does not have resistance or immunity to cold damage, they take extra cold damage equal to your wizard level.

Whiteout

After extensive use of bending ice to your every whim, you understand all of its inner workings. You're able to apply this knowledge by performing grand feats on a monumental scale. As an action, you are able to freeze everything within a 60 foot radius sphere centered around you. This creates sleets of ice and snow on the ground and super chilling the air, rendering the area as difficult terrain. All creatures of your choice takes 3d6 cold damage upon activation and must make a Strength saving throw against your spell save DC or be frozen. While frozen, a creature is considered incapacitated and their speed is reduced to 0 until the end of their next turn.

Furthermore, you create a 30 foot radius sphere of a perpetual blizzard that is centered around and moves with you. When a creature of your choice enters the area for the first time or starts their turn in it, the creature must succeed on a Constitution saving throw against your spell save DC or take cold damage equal to half your wizard level and have its speed halved until the start of its next turn. The area inside the blizzard acts as a heavily obscured area for all creatures except you.

Both the difficult terrain and blizzard lasts for 1 minute or when you end both effects using an action, afterwards you no longer gain the effects of the Frigid Magic feature until you take a short rest. Once this feature is used it cannot be used again until a long rest.