Heart of the Fae Queen. Zephyra is one of the 5 aspects of Tiamat. She's immune to Thunder and Lightning damage. 

Storm Warden. If Zephyra fails a skill check, she can choose to succeed instead 3/day. 

Fae Spellcasting. Zephyra's innate spellcasting ability is Charisma (spell save DC 15). 

Multiattack. Zephyra makes two attacks with her spear.

Greatspear. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 22 (4d6 + 9) piercing damage.

Thunder Strike. (3/day). After a successful hit Zephyra charges her spear with lightning, the target must make a DC 15 Constitution saving throw or be stunned until the end of their next turn.

Tiamat Strike 1/day. The giant hurls a magical lightning bolt at a point it can see within 500 feet of it. Each creature within 10 feet of that point must make a DC 17 Dexterity saving throw, taking 54 (12d8) lightning damage on a failed save, or half as much damage on a successful one.

Spellcasting. The giant casts one of the following spells, requiring no material spell components and using Charisma as the spellcasting ability (spell save DC 17):

At will: [spell]thunderwave[spell], [spell]detect magic

3/day each: [spell]lightning bolt, [spell]fog cloud

1/day each: [spell]control weather

Thunderdome Stance. As a bonus action, Zephyra can change her fighting stance. Her AC increases by 4 and her speed drops to 30.

Full Counter. When a melee is made against Zephyra she can take an opportunity attack against a nearby creature. If Zephyra lands the hit, she can move 10 ft. in any direction.

Storm Parry. When a ranged magic attack hits Zephyra she can use her reaction to reduce damage in half and move 10ft in any direction.

Zephyra has 3 legendary action points that refresh on her turn.

Storm Charge.  (1 point)   Zephyra calls upon her powers to charge her next attack by 1d6, this can stack but is used on her next attack.

Lightning Step.  (2 points)  Zephyra can teleport herself up to 30ft. in an unoccupied space within range. Immediately after she disappears, a bright light flashes in place of where Zephyra was, and each creature within 10ft. must make a Dexterity saving throw, DC(15), or be blinded until their next turn.

Thunder Step.  (3 points)  Zephyra can teleport herself up to 30ft. in an unoccupied space within range. Immediately after she appears, a thunderous boom sounds and each creature within 10 feet of the space she appears in must make a Constitution saving throw, DC(15) taking 3d10 thunder damage on a failed save, or half as much damage on a successful one.