School of Cryomancy

A Wizard who studies a certain aspect/element may go by a different name. One who is proficient in fire techniques goes by Pyromancer, one who studies earth magic may be known as a Geomancer, and one who studies holy or undead techniques are referred to as Photomancer and Necromancer respectively. Though, a wizard who specializes in ice magic is known as a Cryomancer. Also known as Frost Mages, Cryomancers manipulate the crystalline structure of ice and bend it to their will. They're known for being able to freeze water, even the moisture in the air, to create ice for their disposal. Normally known as utility and defensive magic, cryomancy is no stranger to being devastatingly powerful.

Of Ice Body and Mind

Your manipulation of the cold has allowed you to change the properties of spells, as well as use it to acclimate your body to withstand extreme temperatures. 

Starting at 2nd level, you gain resistance to cold damage. Furthermore, you are able to manipulate the properties of spells. When you cast a spell that deals damage, you are able to change the damage typing to cold. You are able to do this a number of times equal to your Intelligence modifier. These charges are regained on a long rest.

At 10th level, your body temperature has lowered to the point of granting resistance to fire damage.
When you reach 14th level, you become an almost living embodiment of ice, gaining immunity to cold damage.

Flash Freezing

With the study of cryomancy you have harnessed the ability to freeze water creating ice that you can manipulate to your will.

At 2nd level, as an action, you gain the ability to freeze a 5 ft. cube of nonmagical water. The water remains frozen for one minute, or you lose concentration as if you were concentrating on a spell. The ice is able to be constantly manipulated, and as a bonus action, you may mold its shape to form objects or structures. The objects or structures you create have hit points equal to your wizard level. At 8th and 14th level, you gain the ability to freeze an area of 15 ft. and 25 ft. cube respectively. You also create the ice out of moisture in the air, though the square footage you are able to manipulate is halved.

When you reach 14th level you gain the ability to freeze magical water and manipulate magical ice. Also, the water remains frozen for up to 1 hour.

Cryostasis

Your body has an autonomous instinctual response to death and will actively seek preservation by flash freezing the moisture in the air around you and in your body.

Beginning at 6th level, when you are rendered unconscious or asleep you are immediately encased in a layer of dense ice. The ice that encases you has hit points equal to your wizard level. When the ice encases you as a result of being reduced to 0 hit points, it will stabilize you as well.

The ice lasts for 1 minute, until it is destroyed, or when you regain consciousness. Once this feature is used it cannot be used again until a long rest.

Absolute Zero

You are able to control the temperature of the ice to an abnormal extreme, even by magical standards.

Starting at 10th level, when you hit a creature that does not have resistance or immunity to cold damage, they take extra cold damage equal to your wizard level.

When you reach the 14th level, you gain the ability to ignore resistances to cold damage.
When you reach 18th level, you are able to treat immunities to cold damage as resistances that aren't ignored.

Ice Age

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.

At 14th level, you gain the ability Ice Age. As an action, you are able to freeze all water molecules in a 60 ft. radius sphere centered around you. This creates sleet of ice and snow on the ground whilst super chilling the air, rendering all area it difficult terrain. All creatures you designate in the sphere must make a Strength saving throw equal to your Spell Save DC or be frozen. While frozen, a creature is considered incapacitated until the end of their next turn.

Furthermore, you create a 30 ft. radius sphere of a perpetual blizzard centered around you. For the duration, when any creature hostile towards you enters the area for the first time or starts their turn in it, they must succeed on a Constitution saving throw or take cold damage equal to half your wizard level and have its speed reduced by 15 feet. All creatures inside the blizzard besides yourself are considered blinded.

Both the difficult terrain and blizzard last for 1 minute, afterwards you no longer gain the effects of Absolute Zero until you take a short rest.
Ice Age can be used once per long rest.