Brood Spawn White Dragon

Ice Walk. The dragon 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 it extra movement.

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Light Sickness. While the dragon is exposed to light from a Light , it has disadvantage on saving throws.

Brood Fever. The dragon is infected with the final stage of brood fever, turning it into a brood spawn. Any creature the dragon infects with this disease gains 1 level of Soul Chill. The levels of soul chill on a creature increase by 1 every day that the creature is infected. While infected by brood fever, a creature's charisma drops by 1 for every day that it was infected. If the number of Soul Chill levels on a creature is higher than that creature's number of hit dice, the creature succumbs to the disease and becomes a brood spawn.

Servant to Father Llymic. The dragon is instinctively friendly to Father Llymic and has advantage on saving throws against being charmed while within 300 feet of him.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage plus 4 (1d8) cold damage.

Claw. Melee Weapon Attack: +13 to hit, reach 7 ft., one target. Hit: 16 (3d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning damage and 2 (1d4) Piercing Damage

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 14 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. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Cold Breath (Recharge 5–6). The dragon exhales an icy blast in a 60-foot cone. Each creature in that area must make a DC 19 Constitution saving throw, taking 54 (12d8) cold damage on a failed save, or half as much damage on a successful one. 

Brood Fever (Recharge 5–6). The dragon exhales in a 60-foot cone. Each creature in that area must make a DC 14 Constitution saving throw, becoming infected with brood fever on a failed save, or taking 13 (2d8 +5) necrotic damage on a successful one. 

The dragon 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 dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.