Accursed Body. Accursed's body unless it is attacked by a non magical weapon or magical weapon that has Adamantine made out of or in the weapon Accursed is Immune to the attack and its effects.

Magic Weapon. Accursed  weapon attacks are all magic.

Amphibious. The Accursed can breathe air and underwater.

Legendary Resistance (3/Day). If the Accursed Dragon fails a saving throw, it can choose to succeed instead.

limited Magic immunity. If Accursed chooses to be affected. He is immune to spells of 4th level or lower. 

Lucky. The Accursed dragon has the lucky feat

Regeneration. Accursed dragon regenerates 30 hit points at the start of his turn

The Accursed dragon is Vulnerable to Ancient Magic 

Multiattack. The Accursed dragon can use his Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 36 (3d12 + 10) piercing damage.

Claw. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 28 (3d8 + 10) Slashing damage.

Twin Tail Blade. Melee Weapon Attack: +6 to hit, reach 20ft., one target. Hit: 24 (6d6 + 7)  Slashing damage. 

Frightful Presence. Each creature of the Accursed Dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 24 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the Accursed Dragon is within line of sight, 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 Accursed Dragon's Frightful Presence for the next 24 hours.

Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons. 

Accursed Breath. The dragon exhales an Accursed breath in an 120-foot cone that is 10 feet wide. Each creature in that line must make a argets must succeed a DC 20 Con save taking 108 (10d8) Magic damage on a failed save, or Half as much on a successful one. roll  if failed the save 1d10 if this attack hits the following curse happens. 1 blinded, 2 petrified, 3 Paralyzed, 4 is exhausted, 5 poisoned, 6 charmed, 7 unconscious, 8 Frightened, 9 restrained and 10 deafened. is the condition this attack curses the individual with.. 

Poison Breath. The Accursed dragon exhales liquid poison in a 120-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 98 (8d6) poison damage on a failed save and is poisoned, or half as much damage on a successful one.

Weakening Breath. The Accursed dragon exhales gas in a 100-foot cone. Each creature in that area must succeed on a DC 24 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws 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. 

Reflective Scale.  If the Accursed Dragon is targeted by a melee attack , a melee weapon attack , or a weapon that requires a ranged attack roll, roll a d6. Only on a 6, 3 or 1 the Accursed Dragon is affected and is hit, If not anything else the effect is reflected back at the combatant as though it originated from the Accursed Dragon, turning the combatant into the target. The target must succeed a DC 19 Dexterity save or take the same damage type and save effect Accursed would of had to do.

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.

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 15 feet of the dragon must succeed on a DC 16  Dexterity saving throw or take 20 (5d8 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Accursed wind (Costs 3 Actions). Accursed summons forth a mighty cursed wind that pushes all targets within a 50 ft cone 80 ft away. Targets must succeed a DC 20 Con Save 98 (10d8) half as much on a successful save.