As the elf exhaled, the area in front of him slowly froze, ice climbing up the orc's legs. He screams out as he gets enveloped in an ice cocoon. 

The young child emerged from the avalanche, a skeletal hand digging him out. He looks at his surroundings. It feels warm again, as it did before he lost consciousness.

The Arctic Sorcery subclass for Dungeons and Dragons Fifth Edition that implements Constitution as it's main spellcasting ability, and that expands the known spells.

Frost Magic

1st-level Arctic Sorcery feature

You learn additional spells when you reach certain levels in this class as described below. Each of these spells counts as a sorcerer spell for you, but it doesn’t count against the number of sorcerer spells you know. Whenever you gain a sorcerer level, you can replace one spell you gained from this feature with another spell of the same spell level. The new spell must be a conjuration or an evocation spell from the sorcerer, warlock, or wizard spell list.

Frost Magic

At 1st level, you learn ice knife, fog cloud, ray of frost

At 3rd level, you learn Snilloc's snowball swarm, spike growth

At 5th level, you learn sleet storm, wall of water

At 7th level, you learn ice storm, elemental bane 

At 9th level, you learn cone of cold, control winds

Cold-Blooded

1st-level Arctic Sorcery feature

Your heritage chills you to the bone, granting you many benefits. You are resistant to cold damage and once you hit 14th level, this becomes an immunity. In addition, you gain a natural armor of 13+Dex. 

Frostbitten

6th-level Arctic Sorcery feature

Starting at 6th level, when you spend any sorcery points as part of casting a spell that deals damage, you may change the spell’s damage type to cold. You also gain the following two abilities.

Freezing Touch: When you cast a cantrip that deals cold damage, add a bonus to that cold damage equal to your Charisma modifier (min. 1).
Arctic Shock: Any time that you cast a spell of level 1 or higher that deals cold damage, you can used an reaction to force a number of enemies that were affected by the spell must make a Constitution saving throw equal to your Spell Save DC. On a failure, a creature is stunned until the end of its next turn. You would then need either a long rest to regain the ability.

Glacier

6th-level Arctic Sorcery feature

At 6th level, your body has now undergone a massive change that causes you to remain the same for years and your lifespan become longer. For every 10 years that pass, your body ages only 1 year, and you are immune to being magically aged.

Frigid Touch

14th-level Arctic Sorcery feature

Your innate attunement to the frigid climate that is your own being has empowered your magical abilities. When you deal cold damage as a result of an ability or a spell, you ignore resistances to cold and do half damage to any creature who would be immune to cold. In addition, when you deal cold damage, you increase the damage by 1d8.

Cold-Blooded Improvement

At 14th level, your resistance to Cold damage becomes an immunity.

Dead of Winter

18th-level Arctic Sorcery feature

Your body has become one with the feeling of Absolute Zero. As an action, your body turns into pure ice, and you shatter, reappearing in a empty space within 30 feet. Everyone in a 30 foot radius from the shatter must make a Dexterity saving throw, taking 5d8 magical piercing damage on a failed save, or half as much on a success. The following turn, howling winds fill the area. Everyone in a 30 foot radius must make a Constitution saving throw, taking 7d8 on a failed save, and half on a successful save. You can only use this ability again after taking a long rest.