Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Undead Fortitude: If damage reduces the demigod to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the demigod drops to 1 hit point instead.

Multiattack. The Zombie Demigod makes two attacks with its slam.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 7) bludgeoning damage plus 7 (2d6) necrotic damage.

Divine Smite. The Zombie Demigod infuses its slam attack with divine energy, dealing an extraHit: 18 (4d8) radiant damage on a hit. The demigod can use this ability up to three times per day. 

Soul Drain Recharge 4-6 1d6. Ranged Spell Attack: +9 to hit, reach 120 ft., one target. Hit: 28 (8d6) necrotic damage. The target must make a DC 16 Constitution saving throw or have its maximum hit points reduced by an amount equal to the necrotic damage dealt. This reduction lasts until the target finished a long rest. The Zombie Demigod then heals by an amount equal to the necrotic damage dealt.

Unholy Aura. The Zombie Demigod emits an aura of dark energy in a 30-foot radius around it. Any creature in the aura that attempts to cast a spell must make a DC 16 Wisdom saving throw or the spell fails and is wasted. The aura remains active until the Zombie Demigod dismisses it as a free action or until it fails a concentration check.

Chill of the Grave. The temperature in the area drops suddenly and painfully cold. Each creature in the area must make a DC 16 Constitution saving throw or take 11 (2d10) cold damage and have its speed halved until the end of its next turn. 

Necrotic Miasma. The Zombie Demigod unleashes a could of noxious, necrotic energy in a 20-foot radius around it. Any creature in the area must make a DC 16 Constitution saving throw or take  11 (2d10) poison damage and be poisoned until the end of its next turn.

Slam. The Zombie Demigod makes one slam attack.  Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 7) bludgeoning damage plus 7 (2d6) necrotic damage.

Divine Blast (Costs 2 Actions). The Zombie Demigod unleashes a burst of divine energy in a 30-foot cone. Each creature in the area must make a DC 16 Dexterity saving throw or take 22 (4d10) radiant damage or half as much damage on a success.

Foul Curse (Costs 3 Actions). The Zombie Demigodtargets on creature within 60 feet of it. The target must make a DC 16 Constitution saving throw or be cursed for 24 hours. While cursed, the target takes  5 (1d10) necrotic damage at the start of each of its turns, and any healing it receives is halved. The curse can only be lifted with a remove curse spell or similar magic.

The Zombie Demigod can take 3 legendary actions per turn, 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. The Zombie Demigod regains spent legendary actions at the start of its turn.

Frost of Death: The demigod unleashes a blast of freezing cold air in a 20-foot radius around itself. Each creature in that area must make a DC 16 Dexterity saving throw or take 44 (8d10) cold damage on a failed save, or half as much damage on a successful one.

Stigmata Spray: The demigod sprays black blood from stigmata wounds at all creatures within a 30-foot radius. Each creature must make a DC 16 Constitution saving throw or take 22 (4d10) poison damage on a failed save and is poisoned for 1 hour. On a successful save, the creature takes half as much damage and isn't poisoned.

Curse of Death: The demigod curses one creature it can see within 60 feet of it. The target must make a DC 16 Wisdom saving throw or have disadvantage on all attack rolls, ability checks and saving throws for 1 minute. Aditionally, at the end of each of its turns, the cursed creature must make a DC 16 Constitution saving throw or take  11 (2d10) necrotic damage.

The Zombie Demigod can take 3 Mythic actions per day, 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. The Zombie Demigod regains spent Mythic actions after a long rest.