Winter warlocks are the mortal agents of the otherworldly entity known as Ithaqua, the Wind Walker. They haunt the coldest corners of the world, where the nights are long and the wind howls louder than the wolves.

Medium humanoid (human)
No. Appearing: 2d3-1, often accompanied by winter-aspected seely wights or itinerant berserkers in their thrall
Hit Dice: 5d8 (23 hit points); saves as a magic-user. Winter warlocks are immune to damage from cold-based spells and abilities.
Armor Class: Low (frost-encrusted furs and hides + average dexterity)
Movement: As a normal, unencumbered human. Winter warlocks are unaffected by snowy or icy terrain. When walking through snow, they can choose to leave no tracks or misleading tracks.
Demeanor: Cunning and callous; occasionally distracted as they listen for Ithaqua’s words on the wind. Bright lights and open flames make them uncomfortable.
Attack: by weapon, usually spears or axes (+3 melee or thrown, 1d6 damage)
Special:

• Boreal Fiends: As their action, the winter warlock makes weird, discordant music. 1d3-1 rounds later, 1d4 boreal fiends appear out of a freezing mist. The boreal fiends will obey the commands of any winter warlock; if none exist, they will disappear back into freezing mist. Boreal fiends can only be summoned once every 24 hours.
• Grip of Winter: As their action, the winter warlock can grab a creature within reach (a +3 melee attack). On a hit, the target suffers 2d6 damage and is grappled by the warlock. Every subsequent round, if the target is still grappled on the warlock’s turn, they suffer another 2d6 damage. Breaking free from the warlock’s grasp requires an opposed Strength check, which the warlock makes with a +5 bonus. After using this ability, there is a 1-in-6 chance it recharges at the start of the warlocks next turn.
• Winds of Limbo: As their action, the winter warlock summons powerful, bitterly cold winds that swirl in a 10-foot radius around them, forcing out creatures that fail a Strength saving throw. The affected area is considered difficult terrain and creatures have disadvantage on missile attacks targeting the warlock. The winds last as long as the warlock maintains concentration. The warlock can end the effect by concentrating the winds into a blast targeting a single creature. If the target fails a Strength or Dexterity saving throw, they are hurled backwards 50 feet; if they strike a solid obstacle before reaching that, they suffer damage as if they had fallen from a height equal to the distance they moved. A warlock can also end the effect early to propel themself into the air, flying a maximum of 5 miles before landing. After using this ability, there is a 2-in-6 chance it recharges at the start of the warlocks next turn.

I Loot the Body (roll 1d8):

1-3: Rawhide pouch of animal grease. A character that slathers this gamy-smelling paste over their body gains Advantage on saving throws to resist cold-based spells and effects. Can also be used as rations in a pinch, but characters with a Constitution score of 12 or less must succeed a Constitution saving throw or become sickened for 1d4 hours after eating. The pouch contains 2d3 applications.
4-5: Ivory effigy: Scrimshawed carving of a humanoid with its head thrown back in a howl. A character that succeeds an Intelligence roll can identify it as a depiction of Ithaqua. May be of interest to scholars or occultists. While in possession of the effigy, a character has a 1-in-20 chance every time they go to sleep that they dream of a wind-swept, frozen wasteland where a giant humanoid figure can be seen prowling on the horizon.
6: Carnivore Mask. A chimerical construction of bones from various predatory animals. The wearer gains the ability to speak and understand the languages of carnivorous animals, but has Disadvantage on all rolls related to interacting with prey animals.
7: A flute made from a human thigh-bone. When played, a boreal fiend will arrive out of a cloud of freezing-cold mist 1d3-1 rounds later. The creature will obey the commands of the flute-player for 24 hours, after which it will disappear back into rapidly dispersing mist. There is no limit to how many times the flute can be use, but unless the player is a winter warlock, there is a cumulative 1-in-20 chance per use after the first that the instrument breaks, releasing all of the summoned fiends to act as they wish.
8: A book bound in human leather containing rambling screeds and unsettling diagrams. A character that succeeds an Intelligence saving throw can discern from the contents the instructions for summoning the Winds of Limbo. Non-spellcasters who study the text can use the ability once per day. Spellcasters can add Winds of Limbo to their list of spells known. Whether or not a character is a magic-user, every time they summon the Winds of Limbo, they must succeed a Wisdom saving throw or lose 1d3 Charisma as Ithaqua claims a piece of their soul.

BOREAL FIEND
Fragments of Ithaqua manifesting on the Material Plane, boreal fiends look like the corpses of humans who have died of exposure – pallid, emaciated, noses and lips frostbitten away, fingertips worn to jagged bone.

Medium outsider
Hit Dice: 1d12 (7 hp); saves as a fighter. Boreal fiends are immune to cold-based damage and effects, but take double damage from fire.
Armor Class: Medium (otherworldly flesh + above average Dexterity)
Movement: 50% faster than an normal, unencumbered human. Boreal fiends are unaffected by snowy or ice terrain.
Demeanor: Malevolent and aggressively hostile. Boreal fiends are immune to fear-based spells and effects.
Attack: Bony claws x2 (+2 melee, 1d8 damage)
Special: Fiendish Frost – As its action, a boreal fiend can unleash a terrible cry, exhaling a 15-foot long conical blast of ice. Creatures in the area of effect that fail a Dexterity saving throw suffer 1d10 damage and have Disadvantage on Strength- and Dexterity-based rolls until the start of the fiend’s next turn from the numbing cold. Targets that succeed the saving throw take half damage and don’t suffer Disadvantage. After being used, this ability has a 1-in-6 chance of recharging at the start of the fiend’s next turn.