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

Dark Blades.  Able produces the blades he uses to attack with at the start of his turn.  The blades appear completely black, and are invisible in darkness.  Able has advantage on attacks made with these blades if the attacks are made in darkness and the target does not have darkvision.  The blades vanish at the end of Able's turn if Able is no longer holding them.  Attacks made with these blades are magical for the purpose of determining resistance or immunity to non-magical damage.

Rage State (5/day).  As a bonus action on his turn, Able can enter a rage state for one minute.  While in a rage state, Able has advantage on Strength Ability Checks and Saving Throws, gains an additional 10 feet of movement, gains a +3 bonus to damage rolls from melee weapon attacks, and gains immunity to bludgeoning, piercing, and slashing damage from non-magical attacks.  This state ends early if Able is knocked unconscious or if Able's turn ends and he has not attacked a hostile creature or taken damage since the end of his last turn.

Relentless Rage. While raging, if Able takes damage that would drop his hitpoints to 0, he can make a DC 10 Constitution saving throw.  On a success, he drops to 1 hitpoint instead.  Every time that Able uses this ability after the first, the DC increases by 5.  The DC resets to 10 if Able takes a short or long rest.

Sarcophagus Regeneration.  If any portion of Able's dead body (or remains) is placed in his sarcophagus,  he is restored to life with all hitpoints and abilities reset in 1d10 days.  Able's sarcophagus is a Large Object with Armor Class 17, 100 hitpoints, immunity to psychic and poison damage, and resistance to fire, cold, necrotic, lighting, as well as bludgeoning, piercing, and slashing damage from non-magical attacks.

Hold Breath.  Able can hold his breath for one hour.

Multiattack. Able makes 4 Dark Blade attacks.  

Dark Blade.  Melee  or Ranged Weapon Attack:  +10 to hit, reach 5 ft. or range 60/120 ft., one target. Hit: 14 (2d8 +5) slashing damage or 17 (2d8 +8) slashing damage if raging.  

Deflect Ranged Damage.  When Able is targeted by a ranged attack and is holding a melee weapon, he can increase his armor class by 5 until the end of the current turn.

Able can take 3 legendary actions, choosing from the options below.  Only one legendary action can be used at a time and only at the end of another creatures turn.  Able regains spent legendary actions at the start of his turn.

Attack.  Able makes one attack with Dark Blade.

Move.  Able moves up to his speed.