Aspect of Tiamat

Discorporation. When Aspect of Tiamat drops to 0 hit points or dies, her body is destroyed but her essence travels back to the true Tiamat in the Nine Hells.

Legendary Resistance (5/Day). If Aspect of Tiamat fails a saving throw, she can choose to succeed instead.

Magic Resistance. Aspect of Tiamat has advantage on saving throws against all other spells and magical effects.

Magic Weapons. Aspect of Tiamat's weapon attacks are magical.

Multiple Heads. Aspect of Tiamat can take one reaction per turn, rather than only one per round.

Regeneration. Tiamat regains 15 hit points at the start of her turn.

Multiattack. Aspect of Tiamat can use her Frightful Presence. She then makes three attacks: two with her claws and one with her tail.

Claw. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 17 (3d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 25 ft., one target. Hit: 20 (3d8 + 6) piercing damage.

Frightful Presence. Each creature of Aspect of Tiamat’s choice that is within 240 feet of Tiamat and aware of her 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 Tiamat's Frightful Presence for the next 24 hours.

Aspect of Tiamat can take 5 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. Aspect of Tiamat regains spent legendary actions at the start of her turn.

Aspect of Tiamat’s legendary action options are associated with her five dragon heads (a bite and a breath weapon for each). Once Aspect of Tiamat chooses a legendary action option for one of her heads, she can’t choose another one associated with that head until the start of her next turn.

Bite. Melee Weapon Attack: +11 to hit, reach 20 ft., one target. Hit: 23 (3d10 + 6) slashing damage plus 11 (3d6) acid damage (black dragon head), lightning damage (blue dragon head), poison damage (green dragon head), fire damage (red dragon head), or cold damage (white dragon head). 

Black Dragon Head: Acid Breath (Costs 2 Actions). Aspect of Tiamat breathes acid in a 90-foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 54 (12d8) acid damage on a failed save, or half as much damage on a successful one.

Blue Dragon Head: Lightning Breath (Costs 2 Actions). Tiamat breathes lightning in a 90-foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 66 (12d10) lightning damage on a failed save, or half as much damage on a successful one.

Green Dragon Head: Poison Breath (Costs 2 Actions). Tiamat breathes poisonous gas in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 56 (16d6) poison damage on a failed save, or half as much damage on a successful one.

Red Dragon Head: Fire Breath (Costs 2 Actions). Tiamat breathes fire in a 60-foot cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.

White Dragon Head: Cold Breath (Costs 2 Actions). Tiamat breathes an icy blast in a 60-foot cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 54 (12d8) cold damage on a failed save, or half as much damage on a successful one.