Angelic Weapons.  Zephriel's weapon attacks are magical. When the solar hits with any weapon, the weapon deals an extra 4d8 radiant damage (included in the attack).

Divine Awareness. Zephriel knows if it hears a lie.

Innate Spellcasting. The solar's spellcasting ability is Charisma (spell save DC 19). It can innately cast the following spells, requiring no material components:

At will: detect evil and good, remove curse (self only)

3/day each:  dispel evil and good, resurrection

1/day each: commune, control weather

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

Radiant immunity: Zephriel wields substance of his fallen god, making him immune to radiant damage 

Phase boss: Zephriel fight in two phases. On the second phase following effects will trigger: 
Phase 2: triggers when zephriel is reduced to 70 hp. He will immidietly gain 200 hp and his max hp is now 200

Fading Light – HP Reduction Each Round  At the start of Zephriel’s turn, he fully heals to max HP. • However, his max HP is permanently reduced by 20 HP every round. • He cannot be healed by any external means. • Once his max HP reaches 0, he collapses, his divine essence fully expended. 

His multiattack will only attack twice, and only within melee range, and "Blazing wings" is unusable.

Vulnerablities: Zephriel will use all his divine light to destroy, making him vulnerable to all damage types, expect radiant

Multiattack. Zephriel makes three attacks: 2x with spear and once with Blazing wings

Spear of the Last light Melee Attack: +12 to hit, reach 5 ft., one target. Hit: 22 (3d6 + 4) slashing damage plus 27 (4d8) radiant damage.

Spear of the Last light. Ranged Weapon Attack: +12 to hit, range 60/120 ft., one target. Hit: 12 (3d6 + 4) slashing damage plus 18 (4d8) radiant damage

Blazing wings: Recharge 3-6

Area Attack (30 ft. sphere, centered on a point Zephriel can see): Each creature in the area must make a DC 14 DEX saving throw.

On a failure, a creature takes 4d6 fire damage and gains 1 stack of "burning".

Burning: The target takes 1d6 fire damage per stack at the start of their turn, until an action is used to extinquish the fire

On a success, the target takes half as much damage and does not gain the Burning condition.

Radiant Bond. After being thrown, spear reappears in Zephriel's hand

Healing Touch (2/Day). Zephriel touches another creature. The target magically regains 20 (4d8 + 2) hit points and is freed from any curse, disease, poison, blindness, or deafness.

Celestal hop: Zephriel vanishes, and walks through the celestial plane, reappearing within 60ft

Judgment Gaze: Zephriel fixes his celestial eyes upon a single target, forcing it to relive their biggest regrets. Target must succeed on a DC18 wisdom saving throw, or get the "restrained condition". Condition lasts until another creature uses "help" action or target succees a new saving throw at the end of his next turn.

PHASE 1: 
Opportunity attack 


PHASE 2:
When Zephriel drops down to 70 hp, he will immediately use his reaction to set his max hp to 200 and regain 200 hit points. He will also gain following reaction:

Counterattacks – The Lonely Warden’s Grief (Reaction, Unlimited Uses) Every time a melee attack hits him, Zephriel immediately retaliates with a counterattack.  

Counterattack: Melee Psychic Strike on Hit:

 Zephriel’s AC reduces by 2/hit

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

PHASE 1:

Celestal hop (1 action): Zephriel vanishes, and walks through the celestial plane, reappearing within 60ft

Judgment Gaze (cost 2 actions): Zephriel fixes his celestial eyes upon a single target, forcing it to relive their biggest regrets. Target must succeed on a DC18 wisdom saving throw, or get the "restrained condition". Condition lasts until another creature uses "help" action or target succees a new saving throw at the end of his next turn. 

PHASE 2:
"I will not fade, god will not fall"

Legendary Actions (3 Per Round) Zephriel can take 3 Legendary Actions per round, choosing from the following:

1. Desperation Attack (Costs 1 Action) • Zephriel makes a reckless strike with his spear, ignoring all defense.

Hit: Melee Attack: +12 to hit, reach 5 ft., one target. Hit: 14 [rollable](4d6);{"diceNotation":"4d6","rollType":"damage","rollAction":"Spear of the Last light"ge. 

Each time he makes this attack, his AC is permanently reduced by 2.