Great Wyrm Red Dragon

Legendary Resistance (3/Day). When the dragon fails a saving throw, it can choose to succeed instead. When it does, it sheds some of its scales, which turn to charcoal. If it has no more uses of this ability, its Armor Class is reduced to 20 until it finishes a long rest.

Searing Heat. A creature that touches the dragon or hits it with a melee attack for the first time on a turn takes 14 (4d6) fire damage.

Volcanic Tyrant. The dragon is immune to the effects of poisonous gases caused by volcanic environments. It also ignores difficult terrain caused by lava.

Seething Rage. When the dragon is first bloodied, it immediately recharges its breath weapon, if its not already available. Its inner flame erupts, burning brightly in its eyes and mouth. After taking damage from its Searing Heat ability, a creature with resistance to fire damage loses it, and a creature with immunity to fire damage reduces it to resistance. Either effect lasts until the start of the creatures next turn.

Innate Spellcasting. The dragons spellcasting ability is Charisma (save DC 22). It can innately cast the following spells, requiring no material components. 3/day each:command, hold person, glyph of warding, wall of fire, 1/day each:antimagic field, dominate monster, storm of vengeance

Multiattack. The dragon attacks once with its bite and twice with its claws. In place of its bite attack it can Spit Fire.

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 32 (4d10 + 10) piercing damage plus 9 (2d8) fire damage.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 28 (4d8 + 10) slashing damage.

Tail. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 23 (3d8 + 10) bludgeoning damage and the dragon pushes the target 10 feet away.

Cruel Tyranny. The dragon snarls and threatens its minions driving them to immediate action. The dragon chooses one creature it can see and that can hear the dragon. The creature uses its reaction to make one weapon attack with advantage. If the dragon is bloodied it can use this ability on three minions at once.

Spit Fire. The dragon targets a creature within 60 feet forcing it to make a DC 22 Dexterity saving throw. The creature takes 22 (4d10) fire damage on a failure or half damage on a success. A creature that fails the save also takes 11 (2d10) ongoing fire damage. A creature can use an action to end the ongoing damage.

Fire Breath (Recharge 5-6). The dragon exhales a blast of fire in a 90-foot cone. Each creature in that area makes a DC 25 Dexterity saving throw taking 98 (28d6) fire damage on a failed save or half damage on a success. A creature that fails the saving throw also takes 11 (2d10) ongoing fire damage. While affected by this ongoing damage it is frightened of the dragon. A creature can use an action to end the ongoing damage.

Tail Attack. When a creature the dragon can see within 10 feet hits the dragon with a melee attack, the dragon makes a tail attack against it.

Taskmaster. When a creature within 60 feet fails an ability check or saving throw, the dragon roars a command to it. The creature can roll a d10 and add it to the result of the roll, possibly turning the failure into a success.

The dragon can take 3 legendary actions. Only one legendary action can be used at a time and only at the end of another creatures turn. It regains spent legendary actions at the start of its turn.

Cruel Tyranny. The dragon uses its Cruel Tyranny action.

Roar. Each creature of the dragons choice within 120 feet that can hear it makes a DC 22 Charisma saving throw. On a failure, it is frightened for 1 minute. A creature repeats the saving throw at the end of its turns, ending the effect on itself on a success. When it succeeds on a saving throw or the effect ends for it, it is immune to Roar for 24 hours.

Wing Attack. The dragon beats its wings. Each creature within 15 feet makes a DC 25 Dexterity saving throw. On a failure, it is pushed 10 feet away and knocked prone. The dragon can then fly up to half its fly speed.