Legendary Resistance (3/Day). If Dominus Supputari Chaco fails a saving throw, he can choose to succeed instead.

Unyielding Essence. Dominus Supputari Chaco is immune to any spell or effect that would alter his form.

Eldritch Essence. Dominus Supputari Chaco is so alien in nature that any creature that attempts to magically or psychically communicate with it or influence it will fail and take 3d8 psychic damage and roll a DC 18 Wisdom saving throw. On a failed save the creature will suffer from level 6 insanity. On a successful save the creature will suffer from level 3 insanity.

Far Realm Energy. Any creature within 120 feet of Dominus Supputari Chaco must make a DC 12 Constitution saving throw or become an aberration with identical stats and abilities under the control of Dominus Supputari Chaco. On a successful saving throw the creature becomes permanently immune to this ability.

Negative Energy Aura. Any non-undead creature that starts its turn within 30
feet of Dominus Supputari Chaco takes 14 (4d6) psychic damage. Furthermore, non-undead creatures can't regain hit points and do not benefit from resistance to
psychic damage while within 30 feet of the Dominus Supputari Chaco. A non-undead creature that were to magically regain hit points must instead make a DC 25
Constitution saving throw. On a failed save, the creature takes necrotic damage equal to the hit points it would have regained.

Psychic Persistence. Creatures with psychic immunity take 1/4 psychic damage from Dominus Supputari Chaco and aberrations controlled by him instead of none at all.

Cruel Mercy. If a creature dies by Dominus Supputari Chaco's hand he can revive them as a aberration under his control with identical stats and abilities by taking an amount of damage equal to the new creatures hit-points. This can only be done if the creature agrees to it or fails a DC 12 Charisma save.

Psychic Storm. Dominus Supputari Chaco can deal 2d12 psychic damage to up to three targets. On a successful DC 23 Intelligence save the creature will only take 1d6 psychic damage. On a unsuccessful save the creature has a 1/3 chance to become unconscious for 30 seconds.

Corrupted Strike. Melee Weapon Attack: +18 to hit, reach 5 ft., 1 target. Hit: 3d10 +9 necrotic damage. Target must roll DC 21 Intelligence or DC 18 Constitution save (targets choice) or have disadvantage on all Intelligence and Wisdom saving throws until after a long rest.

Psychic Glare. Ranged Weapon Attack: +12 to hit, range 50 ft., 1 target. Hit: 6d8 psychic damage. Target must roll DC 24 Intelligence save or be stunned.

Power Absorption. Dominus Supputari Chaco can kill an aberration under his control to gain one of its abilities or special traits for 1 day.

Reflect Energy. When a spell is successfully used on Dominus Supputari Chaco he can chose to take 4d6 necrotic damage (ignoring his resistance) and become unable to use any actions for an amount of turns equal to the level of the spell in order to cause the spell to fail and instantly cast any spell of lower than or equal level in response.

Dominus Supputari Chaco 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 creature's turn. Dominus Supputari Chaco regains 2 spent legendary actions at the start of his turn.

Show True Form (Costs 3 Actions). All targets who can currently perceive the Dominus Supputari Chaco must make a DC 24 Wisdom check or suffer from level 5 insanity. Creatures who pass this check only have to pass a DC 15 Wisdom check if this ability is used again on them. This resets after a long rest.

Summon Aberration. Dominus Supputari Chaco can summon any number of aberrations under his control whose CRs add up to a maximum of 3 multiplied by the number of legendary actions used for this ability. Leftover CR can be used next time Dominus Supputari Chaco uses this ability.

Use Power (Costs 1 Action). Dominus Supputari Chaco uses one of his actions.

Energy Flow (Costs 0 Actions). Dominus Supputari Chaco transfers hit-points between himself and an aberration under his control or between aberrations under his control. 1/2 of the hit-points are lost during the transfer.