Legendary Resistance (5/Day). If the dracolich fails a saving throw, it can choose to succeed instead.

Magic Resistance. The dracolich has advantage on saving throws against spells and other magical effects.

Turn Resistance. The Dracolich has advantage on saving throws against any effect that turns undead.

Invulnerability: If the Dracolich is slain, his spirit immediately returns to its phylactery, a black opal of insignificant size. If there is no reptilian corpse within 90 feet for his spirit to possess, it is trapped within the phylactery until such a time that a corpse becomes available. If his spirit is in its phylactery, destroying that item when a suitable corpse is not within range effectively destroys him. Likewise, the Dracolich is unable to attempt further possessions if his phylactery is destroyed.

Mastery of Elements: The Dracolich can alter an arcane spell when cast so that it utilizes a different element from the one it normally does. This ability can alter only spells with the acid, cold, fire, electricity, or sonic descriptors. The spell's casting time is unaffected and the creature decides whether or not to alter the spell's energy type and chooses the new energy type when he begins casting.

Innate Spellcasting. The dracolich’s innate spellcasting ability is Charisma. It can innately cast the following spells (spell save DC 15), requiring no material components:

At will: darkness, false life, levitate (self only), mage armor (self only), silent image

1/day each: feeblemind, finger of death, prismatic spray, dominate person, psychic scream, stinking cloud, magic circle

Cantrips (at will): eldritch blast, fire bolt, poison spray, mage hand, toll the dead, mind sliver, shocking grasp

1st–7th level (4 7th-level slots): banishment, burning hands, flame strike, hellish rebuke,  scorching ray, counterspell, silence, wall of force

Multiattack. The dracolich can use its Frightful Presence. It then makes four attacks: one with its bite, two with its claws, and casts a spell.

Bite. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus 5 (1d10) lightning damage.

Claw. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Tail. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.

Frightful Presence. Each creature of the dracolich’s choice that is within 120 feet of the dracolich and aware of it must succeed on a DC 18 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 dracolich’s Frightful Presence for the next 24 hours.

Acid Breath (Recharge 5–6). The dracolich exhales acid in a 90-foot line that is 5 feet wide. Each creature in that line must make a DC 20 Dexterity saving throw, taking 66 (12d10) acid damage on a failed save, or half as much damage on a successful one.

The dracolich 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 dracolich regains spent legendary actions at the start of its turn.

Detect. The dracolich makes a Wisdom (Perception) check.

Tail Attack. The dracolich makes a tail attack.

Wing Attack (Costs 2 Actions). The dracolich beats its tattered wings. Each creature within 10 feet of the dracolich must succeed on a DC 21 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone. After beating its wings this way, the dracolich can fly up to half its flying speed.