Ancient Vampiric Half Dracolich Tarrasque

Legendary Resistance (5/Day): If the tarrasque fails a saving throw, it can choose to succeed instead.

Magic Resistance: The tarrasque has advantage on saving throws against spells and other magical effects.

Reflective Carapace: Any time the tarrasque is targeted by a Magic Missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the tarrasque is unaffected. On a 6, the tarrasque is unaffected, and the effect is reflected back at the caster as though it originated from the tarrasque, turning the caster into the target.

Regeneration: The tarrasque regains 50 hit points at the start of its turn if it has at least 1 hit point. If the tarrasque takes radiant damage or damage from holy water, this trait doesn't function at the start of the tarrasque’s next turn.

Rejuvenation: A destroyed tarrasque gains a new body in 1d100 years, regaining all its hit points. At which point it enters a 1000 year slumber before becoming active again.

Siege Monster: The tarrasque deals double damage to objects and structures.

Turn Immunity: The tarrasque is immune to any effect that turns undead.

Undead Nature: The tarrasque doesn’t need air, food, drink, or sleep.

Multiattack: The tarrasque can use its Frightful Presence. It then makes 5 attacks: one with its Bite, two with its Claws, one with its Horns, and one with its Tail. It can replace its Bite with a Swallow attack.

Bite: Melee Weapon Attack: +20 to hit, reach 10 ft., one target. Hit: 29 (3d12 + 10) piercing damage plus 13 (2d12) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the tarrasque regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A creature slain in this way rises the following night as an undead under the tarrasque’s control. If the target is a creature, it is grappled (escape DC 24). Until this grapple ends, the target is restrained, and the tarrasque can't bite another target.

Claws: Melee Weapon Attack: +20 to hit, reach 15 ft., one target. Hit: 28 (4d8 + 10) slashing damage. The target must succeed on a DC 24 Constitution saving throw or be Paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Horns: Melee Weapon Attack: +20 to hit, reach 10 ft., one target. Hit: 32 (4d10 + 10) piercing damage.

Tail: Melee Weapon Attack: +20 to hit, reach 20 ft., one target. Hit: 24 (4d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 24 strength saving throw or be knocked prone.

Frightful Presence: Each creature of the tarrasque’s choice within 120 feet of it and aware of it must succeed on a DC 24 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the tarrasque is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the tarrasque’s Frightful Presence for the next 24 hours.

Dregs of the Devourer (Recharge 9-10): The tarrasque exhales smog in a 120 foot cone. Each creature in that area must make a DC 24 Constitution saving throw, taking 105 (30d6) necrotic damage on a failed save, or half as much damage on a successful one. The target dies if this effect reduces its hit points to 0. A creature slain in this way rises the following night as an undead under the tarrasque’s control. Alternatively, the tarrasque vomits up 2d8 zombies or skeletons, 2d4 minotaur skeletons or ogre zombies, or 1d4 zombie beholders. These undead are allies with the tarrasque and under its control.

Swallow: The tarrasque makes one Bite attack against a large or smaller creature it is grappling. If the attack hits, the target takes the bite damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the tarrasque, and it takes 56 (16d6) acid damage at the start of each of the tarrasque’s turns.

If the tarrasque takes 60 damage or more on a single turn from a creature inside it, the tarrasque must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures which fall prone in a space within 10 feet of the tarrasque. The tarrasque also regurgitates 1d8 zombies or skeletons. If the tarrasque dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

The tarrasque 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. The tarrasque regains spent legendary actions at the start of its turn.

Attack: The tarrasque makes one claw attack or tail attack.

Charge: The tarrasque can move up to half its walking speed then makes an attack with its Horns.

Chomp (Costs 2 Actions): The tarrasque makes one bite Attack or uses its Swallow.

Detect: The tarrasque makes a Wisdom (Perception) check.

Disrupt Life (Costs 3 Actions): Each non-undead creature within 60 feet of the tarrasque must make a DC 24 Constitution saving throw, taking 28 (8d6) necrotic damage on a failed save, or half as much damage on a successful one. The target dies if this effect reduces its hit point maximum to 0. A creature slain in this way rises the following night as an undead under the tarrasque’s control.

Paralyzing Gaze (Costs 2 Actions): The tarrasque fixes its gaze on one creature it can see within 60 feet of it. The target must succeed on a DC 24 Wisdom saving throw against this magic or become 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. If a target's saving throw is successful or the effect ends for it, the target is immune to the tarrasque’s gaze for the next 24 hours.