homebrew by Team Brievary
Innate Spellcasting. The yuki-onna’s innate spellcasting ability is Charisma (spell save DC 17, +9 to hit with spell attacks). The yuki-onna can innately cast the following spells, requiring no material components:
Shapechanger. The yuki-onna can use its action to polymorph into a Medium cloud of mist or snow, or back into its true form. While in mist form, the yuki-onna can't take any actions, speak, or manipulate objects. It is weightless, has a flying speed of 20 feet, can hover, and can enter a hostile creature's space and stop there. In addition, if air can pass through a space, the mist can do so without squeezing, and it can’t pass through water. It has advantage on Strength, Dexterity, and Constitution saving throws, and it is immune to all nonmagical damage. Legendary Resistance (3/Day). If the yuki-onna fails a saving throw, it can choose to succeed instead. Magic Resistance. The yuki-onna has advantage on saving throws against spells and other magical effects. Misty Escape. When it drops to 0 hit points outside its resting place, the yuki-onna transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious, and it gains 50 temporary hit points. While it has 0 hit points in mist form, it can't revert to its yuki-onna form, and it must reach its resting place within 2 hours or be destroyed. Once in its resting place, it reverts to its yuki-onna form. It is then paralyzed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point. Yuki-Onna Weaknesses. The yuki-onna has the following flaw: Forbiddance. The yuki-onna can't enter a residence without an invitation from one of the occupants. Youth Rites. The yuki-onna can't harm humanoid creatures that have not reached adulthood.
Multiattack (Yuki-Onna Form only). The yuki-onna makes two attacks, one of which can be paralyzing touch. Unarmed Strike (Yuki-Onna Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: 8 1d8+4 bludgeoning damage. Paralyzing Touch. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 11 2d6+4 cold damage. The target must succeed on a DC 17 Constitution saving throw or be paralyzed for 1 minute. A creature can repeat the saving throw at the end of each of it's turns. Charm. The yuki-onna targets one humanoid it can see within 30 feet of it. If the target can see the yuki-onna, the target must succeed on a DC 17 Wisdom saving throw against this magic or be charmed by the yuki-onna. The charmed target regards the yuki-onna as a trusted friend to be heeded and protected. Although the target isn't under the yuki-onna's control, it takes the yuki-onna's requests or actions in the most favorable way it can, and it is a willing target for the yuki-onna's draining kiss. Each time the yuki-onna or the yuki-onna's companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the yuki-onna is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.
The yuki-onna can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The yuki-onna regains spent legendary actions at the start of its turn. Move. The yuki-onna moves up to its speed without provoking opportunity attacks. Unarmed Strike. The yuki-onna makes one unarmed strike. Draining Kiss (Costs 2 Actions). The yuki-onna kisses a creature charmed by it or a willing creature. The target must make a DC 17 Constitution saving throw against this magic, taking 20 3d10+4 cold damage on a failed save, or half as much damage on a successful one. The target’s hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.
On initiative count 20 (loosing initiative ties), and while fighting within their l;air, a yuki-onna can take a lair action to cause one of the following effects; it can't use the same effect two rounds in a row:
The region containing a yuki-onna's lair is warped by their magic, creating one or more of the following effects: