Rime Knight

The archetypal Rime Knight embodies the harsh, unforgiving lands they thrive in, bringing a bitter cold to the battlefield. Their enemies struggle to keep moving against the freezing frostbite that takes their extremities.

Frigid Steel

At 3rd level, you can channel the rime around you to take effect in battle.

You can choose to coat your weapon in magical ice. While coated in this way, the weapon is considered magical for the purposes of overcoming resistance and immunity to nonmagical attacks and damage. A coated weapon deals cold damage instead of its usual type, and you cannot be willingly disarmed of this weapon while you hold it.

You can only have one coated weapon at a time, and you can use your bonus action to have the cold relent and disappear from the weapon. If a creature other than you attempts to wield your coated weapon, they take 1d6 cold damage at the start of each of their turns while they hold it.

Winter's Wrath

Also at 3rd level, you harbor a mystical chill within your body.

This chill is represented by Permafrost dice, which is equal to 1d6. As you reach certain levels in this class, the number of Permafrost dice you have increases: you have a total of 2d6 at 5th level, 3d6 at 11th level, and 4d6 at 17th level. You have certain techniques that use these Permafrost dice, as listed below. Some techniques require a saving throw to resist its effects - the saving throw DC for these effects is calculated as follows: 

Permafrost Save DC = 8 + your Proficiency bonus + your Constitution modifier

You can use a number of these techniques a number of times equal to your proficiency bonus, and you regain any expended uses when you finish a long rest.

Frost Armor

As a bonus action, you can expend one use of this feature and give yourself a number of temporary hit points equal to your Permafrost dice plus half your fighter level, rounding up. While you have these temporary hit points, you have resistance to bludgeoning, piercing, and slashing damage.

Glacial Path

As a bonus action, you can expend a use of this feature to increase your movement speed by 10 ft. and leave a trail of frozen ground until the end of your turn. Whatever space you occupy during that turn becomes slick with ice. The icy terrain lasts for 1 minute, or until you use this ability again.

When a creature enters this area for the first time on its turn, or starts its turn there, it must make a Dexterity saving throw or fall Prone.

Winter's Bite

When you hit a creature with a weapon attack, you can expend one use of this feature to deal an amount of cold damage equal to your total Permafrost Dice, and reduce the target's movement speed by half until the end of their turn. A creature can only have a penalty to its speed from this feature once.

Rimeblood

At 7th level, your body has adapted to freezing temperatures.

You gain resistance to cold damage, and you learn the Shape Water cantrip. When casting this spell, you can only use it to freeze water.

Moreover, the cold damage you deal ignores resistance to cold damage, and treats immunity to cold damage as resistance to cold damage, instead.

Avalanche Strike

At 10th level, you learn to strike with the ferocity of an avalanche.

When you hit a creature with a weapon attack, you can choose to freeze creatures around the target. Creatures within 10 ft. of the target (including the target itself) must make a Strength saving throw against your Permafrost Save DC or be Restrained for 1 minute. A creature restrained in this way can use their action to make a Strength (Athletics) check against your Permafrost Save DC - on a success, it is no longer restrained.

You can use this feature twice, and regain any expended uses when you finish a long rest.

Finally, when you use your Action Surge feature, you can use a Winter's Wrath technique without expending a use of that feature on that turn.

Blizzard Soul

At 15th level, your mastery over the bitter cold has nearly reached its apex.

Each technique granted to you by your Winter's Wrath feature has improved.

Glacial Road

All spaces within 5 ft. of where you move when you use your Glacial Path feature become slick with ice. Moreover, your movement doesn't provoke opportunity attacks while using this ability until the end of your turn.

Spiked Frost Armor

While you have temporary hit points from your Frost Armor technique, you can add your Constitution modifier to any weapon damage roll you make.

Winter's Maw

When you hit a creature using your Winter's Bite technique, the target's movement speed is reduced to zero until the end of their next turn, instead of being halved.

Everlasting Frost

At 18th level, the cold power within you has reached the top of its potential.

When you roll initiative and have no uses of your Winter's Wrath techniques left, you regain one use. Moreover, you are now immune to cold damage.