Vampire Mind Flayer Half-dragon Shadow Tarrasque Lich (VMFHSTL)

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

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

Reflective Carapace. Any time the VMFHSTL 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 VMFHSTL 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 VMFHSTL deals double damage to objects and structures.

Living Shadow. While in dim light or darkness, the VMFHSTL has resistance to damage that isn't force, psychic, or radiant.

Shadow Stealth. While in dim light or darkness, the VMFHSTL can take the Hide action as a bonus action.

Sunlight Sensitivity. While in sunlight, the VMFHSTL has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Shapechanger. If the VMFHSTL isn't in sunlight or running water, it can use its action to polymorph into a Tiny bat or a Medium cloud of mist, or back into its true form. While in bat form, the VMFHSTL can't speak, its walking speed is 5 feet, and it has a flying speed of 30 feet. Its statistics, other than its size and speed, are unchanged. Anything it is wearing transforms with it, but nothing it is carrying does. It reverts to its true form if it dies. While in mist form, the VMFHSTL can't take any actions, speak, or manipulate objects. It is weightless, has a flying speed of 20 feet, can hover, and can enter a hostile creature's space and stop there. In addition , if air can pass through a space, the mist can do so without squeezing, and it can't pass through water. It has advantage on Strength, Dexterity, and Constitution saving throws, and it is immune to all nonmagical damage, except the damage it takes from sunlight.

Regeneration. The VMFHSTL regains 20 hit points at the start of its turn if it has at least 1 hit point and isn't in sun light or running water. If the VMFHSTL takes radiant damage or damage from holy water, this trait doesn't function at the start of the VMFHSTL next turn .

Spider Climb. The VMFHSTL can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Vampire Weaknesses. The VMFHSTL has the following flaws:

Forbiddance. The VMFHSTL can't enter a residence without an invitation from one of the occupants.

Harmed by Running Water. The VMFHSTL takes 20 acid damage if it ends its turn in running water.

Stake to the Heart. If a piercing weapon made of wood is driven into the VMFHSTL heart while the VMFHSTL is incapacitated in its resting place, the VMFHSTL is paralyzed until the stake is removed.

Sunlight Hypersensitivity. The VMFHSTL takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Spellcasting. The VMFHSTL is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 5, -5 to hit with spell attacks). The VMFHSTL has the following wizard spells prepared:

Cantrips (at will): mage hand, prestidigitation, ray of frost

1st level (4 slots): detect magic, magic missile, shield, thunderwave

2nd level (3 slots): detect thoughts, invisibility, Melf's acid arrow, mirror image

3rd level (3 slots): animate dead, counterspell, dispel magic, fireball

4th level (3 slots): blight, dimension door

5th level (3 slots): cloudkill, scrying

6th level (1 slot): disintegrate, globe of invulnerability

7th level (1 slot): finger of death, plane shift

8th level (1 slot): dominate monster, power word stun

9th level (1 slot): power word kill

Multiattack. The VMFHSTL 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) necrotic damage. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the VMFHSTL can't bite another target. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the VMFHSTL 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 humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the VMFHSTL's control. 

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

Horns. Melee Weapon Attack: +19 to hit, reach 10ft., one target. Hit: 32 (4d10 + 10) piercing 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 tarrasque'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 VMFHSTL 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 VMFHSTL 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 VMFHSTL, and it takes 56 (16d6) acid damage at the start of each of the tarrasque's turns.

If the VMFHSTL 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. 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.

Multiattack (VMFHSTL Form Only). The VMFHSTL makes two
attacks.
Children of the Night (1/Day). The VMFHSTL magically calls 2d4 swarms of bats or rats, provided that the sun isn't up. While outdoors, the VMFHSTL can call 3d6 wolves instead. The called creatures arrive in 1d4 rounds, acting as allies of the VMFHSTL and obeying its spoken commands. The beasts remain for 1 hour, until the VMFHSTL dies, or until the VMFHSTL dismisses them as a bonus action.

Tentacle. Melee Weapon Attack: +7 to hit, reach 30 ft., one target. Hit: 20 (4d8 + 2) bludgeoning damage. If the target is a Huge or smaller creature, it is grappled (escape DC 15} and takes 9 (1d8 + 5) psychic damage at the start of each of its turns until the grapple ends. The VMFHSTL can have up to four targets grappled at a time.

Mind Blast (Recharge 5-6). The VMFHSTL magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 17 Intelligence saving throw or take 31 {4dl2 + 5) psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Fire Breath (Recharge 5-6). The VMFHSTL exhales fire in a 90-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

The VMFHSTL 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 tarrasque makes one claw attack or tail attack.

Move. The tarrasque moves up to half its speed.

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