Adult devillish dragon

Legendary Resistance (1/Day, or 2/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.

Breath barrage. The dragon makes three breath attacks. It can replace one attack with a use of (A) pain Breath or (B)spellcasting to cast fireball.

Slash. Melee Attack Roll: +11, reach 10 ft. Hit: 5 (2d20 + 6) Slashing damage plus 4 (1d8) Fire damage.

Acid Breath (Recharge 5–6). Dexterity Saving Throw: DC 18, each creature in a 60-foot-long, 5-foot-wide Line. Failure: 85 (10d20) acid damage. Success: Half damage.

Paralysis Breath. Constitution Saving Throw: DC 18, each creature in a 60-foot Cone. First Failure: The target has the [Tooltip Not Found] condition until the end of its next turn, at which point it repeats the save. Second Failure: The target has the [Tooltip Not Found] condition for 10 minutes. This effect ends for the target if it takes damage or a creature within 5 feet of it takes an action to wake it.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 16):

At Will: Detect Magic, Minor Illusion, fireball, Shapechange (Beast or Humanoid form only, no Temporary Hit Points gained from the spell, and no Concentration or Temporary Hit Points required to maintain the spell), [Tooltip Not Found]
1/Day Each: Detect Thoughts, Control Weather

It is always laughing even when dying. It's weak spot is its purple stomach if it is hit on this place it will be blinded for a whole day.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Blazing Light. The dragon uses Spellcasting to cast fireball.

Pounce. The dragon moves up to half its Speed, and it makes one Rend attack.

Acidic air. Dexterity Saving Throw: DC 16, one creature the dragon can see within 120 feet. Failure: 100 (6d20) acid damage, and the target’s Speed is halved until the end of its next turn. Failure or Success: The dragon can’t take this action again until the start of its next turn.

summoning. Summons an army of lost souls to it's aid. can only use this move at half health.

Sleep shield. when sleeping a shield with 1000 health appears over it this shield has no weakness and can wake up the dragon if it's beginning to break.