Adult Irradiated Dragon

Radioactive. Poison damage from this creature bypasses resistance and immunity.

Radiation Poisoning. If the dragon applies the “poisoned” effect to a creature, the creature takes 14 (3d8) poison damage at the end of its turn. If the creature falls to 0 hp after the damage is applied, they melt into radioactive goo.

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

Multiattack. The dragon can use its frighting presence. It then can make 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 7 (2d6) poison damage. The target rolls a DC 18 Constitution saving throw, on a failed save, the target is poisoned for 1d8 minute(s)

Claws. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage

Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning 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 16 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.

Radiation Breath (Recharge 5-6). The dragon exhales a radioactive gas in a 60 ft cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 54 (12d8) poison damage and is poisoned for 1d8 minute(s) on a failed save, or half as much and is not poisoned 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.

Radioactive Aura (Costs 3 Actions). The dragon unleashes a radioactive aura in a 50 ft radius sphere centered around the dragon that deals 66 (12d10) poison damage. The damage is taken at the the start of the round and at the start and end of the dragons 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.