Az, First Blade of Esher, Master of the Seven Crimson Secrets, Chief of Eternal Darkness, Child of the Trickster God

Legendary Resistance. 2/day.

Child of the Trickster God. Az does not provoke opportunity attacks, attack rolls outside of 5ft of Az have disadvantage unless the target has blindsight or truesight. In addition when Az is subjected to an effect that allows him to make a Dexterity saving throw to take only half damage, he instead take no damage if he succeeds on the saving throw, and only half damage if he fails.

First Blade of the Crimson Blades. Az may take a reaction on every turn rather than every round.

Infernal Smite. Az may expend a spell slot when he hits with an attack. He deals an extra 3d8 radiant for 1st level and an additional 1d8 per level above 1st.

Shadow-Strike. If Az has advantage on an attack or has an ally within 5ft of the target, he may deal an extra 5d6 damage with the weapon once per turn.

Chief of Eternal Darkness. Az has advantage on stealth in dim light or darkness.

Sentinel at Death's Door. Az may make opportunity attacks even if the target disengages. If Az hits with an opportunity attack the targets speed is reduced to zero until the end of its turn. Additionally when a creature within 120ft of Az makes death saves the target may either pass on a roll or an 8 or higher or a 14 or higher, depending on Az's whim.

Spellcasting. The Az is a 9th level spellcaster. (spell save DC 20, +12 to hit with spell attacks and a modifier of +6). Az has the following Warlock spells he can innately cast:

1st level (4 slots): detect magic, identify, hellish rebuke, cure wounds, protection against good and evil

2nd level (3 slots): pass without trace, knock, invisibility

3rd level (3 slots): Fireball, Counterspell, Revivify 

Hellish Vigor. Az has a pool of 80 hit points that as an action he can distribute some or all to a creature he can touch.

The Seven Crimson Secrets. Az shouts seven vile words causing a ripple of unreality around him. Each creature within 60ft of Az must make a Wisdom saving throw DC20 or take 12d8 psychic damage and be stunned for on minute. Creatures that pass the save take half as much damage and aren't stunned. Stunned creatures may repeat the save at the end of their turn. (Recharge 6).

Multiattack. Az may make three attacks that can either be with his hellfire blade or with the Devils Plunder.

Hellfire Blade. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 12 (1d8 + 8) Slashing damage and 10 (3d6) fire damage.

The Devils Plunder. Ranged Weapon Attack: +14 to hit, range 60/120 ft., one target. Hit: 18 (2d8 + 8) Radiant damage. If a 19 or 20 is rolled to hit with this weapon a enchanted coin is fired from the barrel of the Devils Plunder. Ignore the normal crit rules and the target must make a DC 20 Con save if it fails it becomes under the effects of the Flesh to stone spell and is counted as having failed the first save. (Reload 6)

Eshers Whip. As a bonus action Az may lash out at a target within 30ft with a semi-corporeal whip. The creature must make a DC20 Con save, on a fail Az drains and absorbs 2d3 levels of spell slots or 2d3 hit dice. If the target has less than the required hit dice the target gains a level of exhaustion. (Recharge 4-6)

Shadow Step. Az may teleport up to 30ft and take the hide action.

The Infernal Wings of Ashnod the Grim. Ripped from the back of a greater demon of the Skulltaker these wings fused to the back of Az in their semi corporeal state. As a reaction Az may bring the hellfire and bronze wings into the material plane and use them for protection. Az loses his fly speed until the end of his next turn and his movement speed is reduced to 30ft. as material physics cannot allow him to fly with these wings, however until the end of the same period he gains a +5 to AC and immunity to fire. This ability cannot be activated if Az does not have a fly speed.

Phase Step. As a reaction to becoming a target of an attack Az may teleport 30ft to an unoccupied space of dim light or darkness causing the attack to miss. He may only use this this ability once a round.