Vampire-Tarrasque-Demilich

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

Magic Resistance. The Vampire-Tarrasque-Demilich has advantage on saving throws against spells and other magical effects.

Reflective Carapace. Any time the Vampire-Tarrasque-Demilich 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.

Siege Monster. The Vampire-Tarrasque-Demilich deals double damage to objects and structures.

Life Steal. The Vampire-Tarrasque-Demilich regains hitpoints equal to the damage he deals each time he makes a bite attack.

Spellcasting. The Vampire-Tarrasque-Demilich is a 9th-level spellcaster. Its
spellcasting ability is Intelligence (spell save DC 15, +7
to hit with spell attacks). The vampire has the following
wizard spells prepared:
Cantrips (at will) :
mage hand, prestidigitation, ray of frost
1st level
(4
slots):
comprehend languages,fogcloud, sleep
2nd level (3 slots):
detect thoughts, gust of wind,
mirror image
3rd l evel (3 slots):
animate dead, bestow curse, nondetection
4th lev el (3 slots):
blight, greater invisibility
5th level (1 slot) :
dominate...

Multiattack. The Vampire-Tarrasque-Demilich can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 36 (4d12 + 10) piercing damage. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the Vampire-Tarrasque-Demilich can't bite another target.

Claw. Melee Weapon Attack: +19 to hit, reach 15ft., one target. Hit: 28 (4d8 + 10) slashing damage.

Tail. Melee Weapon Attack: +19 to hit, reach 20ft., one target. Hit: 24 (4d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be knocked prone.

Frightful Presence. Each creature of the Vampire-Tarrasque-Demilich’s choice within 120 feet of it and aware of it must succeed on a DC 17 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 Vampire-Tarrasque-Demilich 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.

Swallow. The Vampire-Tarrasque-Demilich makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite's 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 Vampire-Tarrasque-Demilich takes 120 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. 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 Vampire-Tarrasque-Demilich can take 3 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 Vampire-Tarrasque-Demilich makes one claw attack or tail attack.

Move. The Vampire-Tarrasque-Demilich moves up to half its speed.

Chomp (Costs 2 Actions). The Vampire-Tarrasque-Demilich makes one bite attack or uses its Swallow.

Flight (Costs 3 Action). The Vampire-Tarrasque-Demilich gains a flying speed of 45ft for 5 minutes