Coldfire Wyvern

Flyby. The coldfire phoenix doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Siege Monster. The coldfire phoenix deals double damage to objects and structures.

Cold Form. The coldfire phoenix radiates a cold energy around it. Any creature that touches the coldfire phoenix or hits it with a melee attack while within 5 feet of it takes 5 (1d10) cold damage.

Blizard Death. When the coldfire phoenix dies, it crystalizes into ice and shatters into thousands of shards. A blizzard forms, centered on the phoenix in a 1 mile radius. Each creature within 120 feet of the phoenix when it dies must make a DC 18 Constitution saving throw or take 20 (4d10) cold damage and 20 (4d10) slashing damage or half as much damage on a successful one. The blizzard is supernatural weather, lasting for 2d4 weeks.

Cold Disaster. Any creature that is killed by the Cold Wind or Stinger abilites will rise as a Coldfire Zombie in 1d4 rounds.

Multiattack. The wyvern makes two attacks: one with its bite and one with its stinger. While flying, it can use its claws in place of one other attack.

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Stinger. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage. The target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Cold Wind (Recharge 5-6). The coldfire wyvern lands and flaps its wings, causing cold air to rush in a 60 foot cone. Each creature in that area must make a DC 19 Dexterity saving throw or take 20 (4d10) cold damage and 20 (2d10) slashing damage  be frozen in place, reducing that creatures movement speed to 0 until the start of the wyvern's next turn. On a successful save, the creature takes half as much damage and its movement speed is reduced by half until the start of the wyvern's next turn.