The Winter Mark

Winter Marked sorcerers are physically marked in some way.  It can take the form of blue lines or designs anywhere on their body, but other versions could exist. This Mark is often placed in prolonged extreme cold, which the new marked person miraculously survives with little damage.  The Marks are definitely magical in nature, granting the marked person with strong magic reflecting its icy origins.  

Marks are extremely rare, and as such little is known about them, or their origins.  What that specific origin of the Mark is, whether natural or not, will be up to the sorcerer to find out.

The Mark’s Protection

At Lv. 1, the Winter Mark grants it’s users an icy protective coating.   After you cast a spell of first level or higher that is an Abjuration spell or a spell that does cold damage, you gain temporary hit points equal to your Charisma modifier (min. 1).  These temporary hit points last for 1 hour.  Additionally, you are resistant to cold damage.

Savaging Cold

At Lv. 6, you learn how to chill deeper than most other casters.  Once per turn, when you cast a spell dealing cold damage add your Charisma modifier (min. 1) to the damage it deals on a hit.  You may do this once per round.  Your spells may ignore resistances to cold damage.

Flash Freeze

At Lv 14, you learn to freeze creatures thoroughly and quickly.  Once per long rest, when a creature of Huge size or smaller you can see takes cold damage, you may use your bonus action, and the target must make a Constitution saving throw against your spell DC.  On a failure, they are paralyzed, frozen solid, for one turn.  After that they must take an action to make a Constitution saving throw to end the effect.

Winter Unending

The Mark saved you before, and now you have mastered it to save yourself many times over.  Once per long rest, as an action you may enter a protective magical ice block.  You are immune to damage and effects (except healing effects, which work as normal) while in the ice block.  The only actions you can take are an action to regain 4d10 hit points, or a bonus action to break free from the block.  No other actions are possible.  While you are aware of what is happening outside the ice block, your concentration effects end on activation.

If you have not used this ability when you are knocked unconscious, but not killed outright, this ability automatically triggers.

The ice block can only be broken by you, taking 200 points of fire damage, an 8th level Disintegration spell, or a 7th level Dispel Magic spell.