Corrupted Soul Mercury Dragon (Santa)

Ice Walk. Santa can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost him extra movement.

Legendary Resistance (3/Day). If Santa fails a saving throw, he can choose to succeed instead.

Amorphous. The dragon can move through a space as narrow as 1 inch wide without squeezing.

Liquid Bodied. This gives the dragon an Immunity to Slashing, Piercing, and Bludgeoning Damage. It also makes the Adult Mercury Dragon have a Resistance against Poison and Acid Damage

Liquid: Anyone who attacks the dragon with a physical attack must make a DC 15 Constitution save or be poisoned.

Amphibious. The dragon can breathe air and water.

Multiattack: The dragon makes three attacks: one with its bite and two with its claws.

Bite: Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (1d8 + 4) piercing damage and 5 (1d14) acid damage.

Claw: Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (1d6 + 4) slashing damage and 4 (1d4) acid damage.

Tail: Melee Weapon Attack: +7 to hit, reach 15 ft., one target. Hit: 13 (1d8 + 4) bludgeoning damage and 4 (1d4) acid damage.

Special Abilities

Cookie Breath (Recharge 5-6): Santa exhales a stale cookie and rotten milk-scented blast in a 30-foot cone. Each creature in that area must make a DC 14 Constitution saving throw, taking 18 (4d8) cold damage on a failed save, or half as much damage on a successful one.

Jolly Evil: Each creature of Santa's choice that is within 60 feet of Santa and aware of him must succeed on a DC 12 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).
In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Quicksilver Form. As a bonus action, the dragon takes on a fluid-like appearance. While in this form, it ignores difficult terrain, it can move through a space as narrow as 1 inch wide without squeezing, its speed is increased by 20 feet, and all opportunity attacks against it have disadvantage. Also, while in this form, it can spend 5 feet of movement to no longer be grappled, prone, or restrained. Finally, while in this form, it cannot use its breath weapon, fly, use its Wing Attack legendary action, or cast spells that require somatic components. It can return to its normal form by using this feature again.

He Knows When You've Been Bad Or Good: Santa pulls a present out of his sack and throws one of the following presents at random, choosing one target it can see within 60 feet of it:

1: Toy Soldiers: Spawns 1d4 Toy Soldiers that each have 1 hit point and take their turn on Santa's initiative. Sword attack: +1 to hit, 1d4+1 slashing damage.

2: Coal: Coal rains down in a 30ft column from where the present was thrown. Deals 3d6 bludgeoning damage.

3: Bicycle: Spawns a bicycle that can be used as a vehicle that has a 60ft movement speed.

4: Puppy: Spawns a puppy that is super adorable. Any creature within 15ft must make a DC 15 Charisma save or be charmed by the puppy for 1 minute. Creatures can repeat the save at the end of each of their turns.

5: Train: Spawns a train that travels in a 30ft circle. This area becomes difficult terrain. Each creature that enters the area for the first time must make a DC 15 Dexterity saving throw or be knocked prone.

6: Dolls: Spawns 1d4 dolls that stand up on their own and stare at any target they choose. Any creature they stare at must make a DC 15 Wisdom saving throw or be frightened of the doll for 1 minute. A creature can repeat this saving throw at the beginning of each of their turns.

7: Puzzle: Spawns a puzzle that looks a bit tricky. The creature this Spawns in front of must make an DC 15 Intelligence saving throw or they're forced to spend their next turn trying to solve the puzzle. They can choose to give up on the puzzle on their next turn.

8:  mistletoe:

• Saving Throw: The target must succeed on a DC 14 Wisdom saving throw or be charmed by Santa for the duration. If the target is fighting Santa or his allies, it has advantage on the saving throw.

• Charmed Condition: While charmed by this spell, the target regards Santa as a friendly acquaintance. When the spell ends, the creature knows it was charmed by Santa.

9: Tinsel: Tinsel digs into their flesh and is restrained.The target must make a DC 14 Dexterity saving throw. On a failed save, the creature takes 1d4 piercing damage On a successful save, the creature takes half damage and is not restrained.

10: CANDY!: Spawns candy that heals 2d6 hit points.

He Makes a List and Checks It Twice (Recharge 6): Santa magically learns the alignment and surface thoughts of all creatures within 60 feet of him. This effect lasts until the end of Santa's next turn. Creatures detected as having malicious or evil intentions must make a DC 14 Wisdom saving throw or be cursed with a -2 penalty to all attack rolls, saving throws, and ability checks for 1 minute. Creatures detected as having good or neutral intentions receive a +2 bonus to all attack rolls, saving throws, and ability checks for 1 minute.