Alt-Ameara

Amphibious. The dragon can breathe air and water.

Living shadow. While in dim light or darkness, Ameara has resistence to damage that isn't force, psychic or radiant.

Shadow Stealth. While in dim light or darkness, Ameara can take the hide action as an action or bonus action.

Sunlight sensitivity. While in sunlight, Ameara has disadvantage on attack rolls, as well as wisdom (Perception) checks that rely on sight.

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

Random Weapon table: 
Rarity. Start by rolling 1d4 when using a portal (1 = rare, 2 = very rare, 3 = legendary, 4 = artefact)
If rare(1) is rolled, add +1 to damage. If very rare(2) is rolled, add +3 to damage. If legendary(3) is rolled, add an additional type of damage (1d10) and +3 to damage, overcomes all resistances to non-magical attacks. If artefact(4) is rolled, add an additional type of damage (1d10), a secondary damage type (2d8) and +3 to damage, overcomes all resistances to non-magical attacks.
Weapon. Roll a second d4 for weapon type. (1 = sword, 2 = pike, 3 = axe, 4 = hammer) Feel free to add additional flavour, a sword could be a longsword or great sword, a pike could also be a lance or a halberd. However damage remains the same.
If Sword (1) is rolled, the weapon deals 1d6 slashing damage. If Pike (2) is rolled, the weapon deals 1d8 piercing damage. If Axe (3) is rolled, the weapon deals 1d10 slashing damage. If Hammer (4) is rolled, the weapon deals 1d12 bludgeoning damage.
Damage types. To determine any additional damage types, roll a d10. (1 = acid, 2 = cold, 3 = fire, 4 = force, 5 = lightning, 6 = necrotic, 7 = poison, 8 = psychic, 9= radiant, 10 = thunder.)
Example, the portal attack hits, the first d4 is rolled giving a 3 the second is then rolled giving a 4 , because the weapon is legendary we must also roll a d10 from which we get a 5, the damage is then. 1d12 + 3 Bludgeoning Damage & 1d10 + 3 Lightning Damage.

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

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 21 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 dragon's Frightful Presence for the next 24 hours.

Breath Weapons (Recharge 3); The dragon uses one of the following breath weapons.

Death Breath. The dragon exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 36 (7d10) Necrotic damage on a failed save, or half as much damage on a successful one. 

Weakening Breath. The dragon exhales gas in a 60-foot cone. Each creature in that area must succeed on a DC 21 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.

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).
In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Human form

In her human form, Ameara now dressed in black plate amour carrying a black blade and a purple visor denoted with red markings. In this form she is about 5ft 8, however still contains the same power of her true form. 

Multi-Attack. Ameara is able to make three attacks with her great-sword. Or two attacks and cast one spell of no level higher than 3.

Great-Sword. Melee Weapon Attack: +14 to hit, reach 5ft, single target. Hit:18(2d8+8) any one's or twos are allowed to be re-rolled as part of these attacks.

Blade-Beam (EXCALIBAAAAAAAAH) (Recharge 6); Ameara raises her blade into the air as a beam of dark and fiery light ignites the heavens. this 15ft wide, 180ft long beam of light can then be discharged 3 times until the blade is summoned again. Creatures caught in this line of fire must make a DC 24 DEX save or take 3d10 fire damage and 4d10 necrotic damage. 

Enkidu, The chains of Heaven.  (Action or Reaction) (5 round recharge) 100ft range, single target.
You summon 10 golden chains from golden portals each with a range of 20ft, these chains cannot be targeted by a magic spell. Player must make a DC 27 DEX save as the chains coil and pierce the targeted creature on a failed save (Dealing 1d6 magical piercing damage per chain.), causing the creature to become restrained. You can break free with a DC 25 STR saving throw (+1 for each chain used), grapple rules apply here. (Each chain has an AC: 21 and HP: 35, destroying a chain causes it to recoil into the portal it came from.) 

The Gates if Babylon. (Initial Action, Bonus action after) (3 per day)
You summon 6 golden portals, within a 120ft radius of yourself. These portals, can then be activated with an action or a bonus action. Each portal has three charges, once used the portal closes. When using a portal, you must make an attack roll against the creature you have targeted. The portal then fires a random weapon (of at-least rare or above rarity).
Note: If a 20 is rolled to hit, then the weapon explodes on impact, any creature in a 20ft radius of the targeted creature must make a DC 21 DEX save or take 3d6 fire damage, or another type if the weapon is legendary or higher grade, double damage does not happen however the targeted creature automatically fails the save.

Counter Attack. If a creature makes a melee attack on Ameara while she is in her human form and misses, Ameara is able to parry and make an attack back. (Human form only.)

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 10 feet of the dragon must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Human form only

Use of special move (Costs 3). Blade Beam, Enkidu or Gates of Babylon.

Enhanced perception (Costs 3). Ameara can use as many reactions this turn as she wishes. (Human form only)