Voidborn Resilience. Sangr'koth has advantage on saving throws against spells and other magical effects. Additionally, when Sangr'koth is reduced to 0 hit points, he instead drops to 1 hit point unless he was killed by radiant damage.

Mark of the Blood Moon. Sangr'koth can summon a blood-red eclipse that envelops the land in a 1-mile-radius sphere. For the next hour, enemies within this radius are imposed with disadvantage on Constitution saving throws, and Sangr'koth deals an extra 14 (4d6) necrotic damage on all attacks. Once used, this feature cannot be used again for 7 days.

Brutality of the Omen Sword. Sangr'koth's Bastard Sword of Blood Omen deals necrotic damage that bypasses resistance and immunity, and each successful attack increases his hit points by an amount equal to half the damage dealt. In addition, for every enemy killed by the sword, Sangr'koth permanently increases his Strength score by 1, up to a maximum of 35.

Legendary Resistance (5/Day). If Sangr'koth fails a saving throw, he can choose to succeed instead.

Multiattack. Sangr'koth makes four attacks: two with his Bastard Sword of Blood Omen and two with his Fist of Ruin.

Bastard Sword of Blood Omen. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 19 (6d10 + 12) slashing damage plus 18 (4d8) necrotic damage. On a critical hit, the target must succeed on a DC 22 Constitution saving throw or their soul is drained, killing them instantly.

Fist of Ruin. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 30 (4d8 + 12) bludgeoning damage. The target is knocked prone unless they succeed on a DC 23 Strength saving throw.

Voidstep (Recharge 5-6). Sangr'koth teleports to an unoccupied space within 100 ft. of his current location. Upon arriving, he unleashes a shockwave in a 30-ft. radius. All creatures within the area must succeed on a DC 26 Dexterity saving throw or take 45 (10d6) force damage and be pushed 20 ft. away.

Blood Unleashed (Recharges on a Long Rest). As a bonus action, Sangr'koth can enter a Blood Fury, granting him advantage on all attack rolls and forcing attackers to succeed on a DC 26 Constitution saving throw or suffer 33 (6d10) necrotic damage when they hit him. This Fury lasts for 10 minutes or until Sangr'koth drops below 50 hit points.

Sangr'koth can take 5 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. Sangr'koth regains spent legendary actions at the start of his turn.

Move. Sangr'koth moves up to his speed without provoking opportunity attacks.

Voidstrike. Sangr'koth makes one Bastard Sword of Blood Omen attack.

Voidcharge. Sangr'koth teleports up to 30 ft. to a space he can see, and if he appears next to a creature, he can make one Fist of Ruin attack.

Devour Magic (Costs 2 Actions). Sangr'koth consumes a spell or magical effect within 60 ft., ending it immediately. For each spell level consumed, he regains 20 hit points.