Quick Draw. Jack has advantage on initiative rolls.

Legendary Resistance (3/day). If Jack fails a save, he can choose to succeed instead.

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

Mage Slayer. When Zero Jack damages a creature concentrating on a spell,  that creature has disadvantage on the saving throw it makes to maintain its concentration. 

Desperation. If Jack is reduced to 0 hit points, he doesn't die. He gouges out his own eyes as a sacrifice to Yawg, regains 200 hit points, recharges Fan the Hammer, summons his Nightmare mount, and can use his Mythical Actions.

Multiattack. Zero Jack attacks three times with either his Chimera Revolver or Wasteland Dagger.

Wasteland Dagger. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 4d4 + 7 slashing damage, and the target must make a DC 19 Constitution saving throw, taking 8d10 poison damage on a failed save, or half as much damage on a successful one. On a failure, the target is also poisoned for 1 minute. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Chimera Revolver. Ranged Weapon Attack: +15 to hit, range 100/400 ft., one target. Hit: 4d10 + 8 piercing damage, plus one of the following effects:

1. Viper Spit. The target must make a DC 19 Constitution saving throw, taking an additional 10d6 acid damage on a failed save, or half as much damage on a successful one.

2. High Noon. The target takes 2d10 radiant damage. In addition, the target and all other creatures within 20 feet of it must each make a successful DC 19 Dexterity saving throw or be blinded until the end of Jack’s next turn.

3. Stampede Shot. The target and each creature within 20 feet of it must make a DC 19 Constitution saving throw, taking 4d12 thunder damage on a failed save, or half as much damage on a successful one.

4. Pitfall Bolas. The target must make a successful DC 19 Dexterity saving throw or be restrained for 1 hour by heavy bolas. A restrained creature can escape by using an action to make a successful DC 19 Dexterity or Strength check.

5. Shock Treatment. The target takes 6d10 lightning damage and must make a successful DC 19 Constitution saving throw or be paralyzed for 1 minute. The paralyzed target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

6. Hellhound. The target must make a successful DC 19 Dexterity saving throw or take 10d10 fire damage, half as much on a successful save. The target dies if reduced to 0 hit points.

Fan the Hammer (Recharge 5-6). Jack fires a storm of infernal bullets in a 60 ft. cone. Each creature in that area must make a DC 19 Dexterity saving throw, taking 20d6 magical piercing damage on a failed save, or half as much damage on a successful one.

Mirage Cloak. The Zero Jack can use a bonus action to become invisible. Any equipment he wears or carries is also invisible as long as the equipment is on his person. This invisibility ends immediately after Jack makes an attack roll or is hit by an attack.

Countershot. Zero Jack makes a revolver attack against a target casting a spell within range. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, it must make a Constitution saving throw of 10 + the spell's level. On a failure, the spell has no effect.

(MYTHIC) Zero Sum. When it is reduced to 15 hit points or fewer, Zero Jack causes himself to explode. All other creatures within 30 feet of him must each make a DC 19 Dexterity saving throw, taking 5d8 fire damage plus 5d8 thunder damage on a failed save, or half as much damage on a successful one. This explosion destroys Jack, his dagger, and his revolver.

Jack 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. Jack regains spent legendary actions at the start of his turn.

Revolver. Jack makes a revolver attack.

Dynamite. Jack places a dynamite trap, dealing 6d6 fire damage to a creature passing within 5 ft of it, half on a DC 19 Dex save.

Summon Hellhound(Costs 2 Actions). Jack summons 1d4 Yawgspawn Hellhounds.

Twin Shot. Jack makes two revolver attacks.

Stampede. Jack's Nightmare moves it's speed without provoking opportunity attacks. Jack can make a dagger attack if he passes within range of another creature.

 Void Scream (Cost 2 Actions). The mouths on Jack open an let out a shattering scream. Up to 3 creatures within 90 ft must make a DC 19 Con save or take 8d6 psychic damage, half as much on a success. On a failure, the creature subtracts a d6 from attack rolls and saving throws until Jack's next turn.