Adult Red Thaetar

Arcane Resistance (Recharge 4–6). One of the Thaetar's biggest advantages is their resistance against any magic cast within 15 to 10 feet of them, causing any magic attacks that enter within the said field will only cause half the damage.

Shapechanger. The Thaetar can use its action to polymorph into a dragonkin-humanoid hybrid or into a Thaetar, or back into its true form, which is humanoid. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Multiattack. Like a Dragon, the Red Thaetar possesses the ability to strike three times: once with it's bite and twice with its claws.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 12 (2d10 + 6) piercing damage plus 6 (1d6) of breath weapon damage.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 8 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 10 (2d8 + 6) bludgeoning damage.

Fire Breath (Recharge 5–6). The Red Thaeter exhales fire in a 60-foot cone. Each creature in that area must make a DC 20 Dexterity saving throw, taking 53 (15d6) fire damage on a failed save, or half as much damage on a successful one.

Wing Shield. It can use its wings to deflect non-magical attacks.

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

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 14 Dexterity saving throw or take 10 (2d6 + 6) bludgeoning damage and be knocked prone.