Wands of Orcus. The wand has 70 charges, and any of its properties that require a saving throw have a save DC of 18. While holding it, the swarm can use an action to cast animate dead, blight, or speak with dead. Alternatively, they can expend 1 or more of the wand's charges to cast one of the following spells from it: circle of death (1 charge), finger of death (1 charge), or power word kill (2 charges). The wand regains ld4 + 3 charges daily at dawn.

While holding the wand, the swarm can use an action to conjure undead creatures whose combined average hit points don't exceed 5000. These undead magically rise up from the ground or otherwise form in unoccupied spaces within 400 feet of the swarm and obey there commands until they are destroyed or until they dismisses them as an action. Once this property of the wand is used, the property can't be used again until the next dawn.

Innate Spellcasting. The swarms spellcasting ability is Charisma (spell save DC 23, +15 to hit with spell attacks). they can innately cast the following spells, requiring no material components:

At will: chill touch (17th level), detect magic

30/day each: create undead, dispel magic

10/day: time stop

Legendary Resistance (140/Day). If the swarm fails a saving throw, they can choose to succeed instead.

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

Magic Weapons. The swarms weapon attacks are magical.

Master of Undeath. When the swarm casts animate dead or create undead, they chooses the level at which the spell is cast, and the creatures created by the spells remain under there control indefinitely. Additionally, they can cast create undead even when it isn't night.

Amphibious. The swarm can breathe air and water.

Freedom of Movements. The swarm ignores difficult terrain, and magical effects can't reduce there speed or cause them to be restrained. they can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Siege Monsters. The swarm deals double damage to objects and structures.

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a gargantuan tiamat. The swarm gain temporary hit points. 

Reflective Carapace. Any time The swarm 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 3, The swarm is unaffected. On a 4,5,6, The swarm is unaffected, and the effect is reflected back at the caster as though it originated from The swarm, turning the caster into the target.

Discorporation. When the swarm drops to 0 hit points or dies, there bodies are destroyed but there essence travels back to there domain in the Nine Hells, and they are unable to take physical form for a time.

Innate Spellcasting (30/Day). The swarm can innately cast divine word (spell save DC 26). there spellcasting ability is Charisma.

Limited Magic Immunity. Unless they wishes to be affected, The swarm is immune to spells of 6th level or lower. they have advantage on saving throws against all other spells and magical effects.

Magic Weapons. The swarm's weapon attacks are magical.

Multiple Heads. The swarm can take one reaction per turn, rather than only one per round. they also have advantage on saving throws against being knocked unconscious. If they fail a saving throw against an effect that would stun a creature, one of there unspent legendary actions is spent.

Regeneration.  The swarm regains 300 hit points at the start of there turn.

Multiattacks. The swarm can use there Frightful Presence. they then make one hundred and forty attacks: twenty with there claws and ten with there dragon tails. ten with there tarrasque bites, twenty with there tarrasque claws, ten with there horns, and ten with there tails. they can use there Swallow instead of there bites. the swarm makes twenty Wand of Orcus attacks, make ten demon tails attacksThe swarm makes thirty tentacle attacks or make ten bites attacks, each of which they can replace with one use of Flings.

Wands of Orcus. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) bludgeoning damage plus 13 (2d12) necrotic damage.

demonTails. Melee Weapon Attack:+16 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) piercing damage plus 9 (2d8) poison damage.

dragon Claws. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 130 (40d6 + 10) slashing damage.

dragon Tails. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 170 (40d8 + 10) piercing damage.

Frightful Presence. Each creature of The swarm’s choice that is within 720 feet of The swarm and aware of them must succeed on a DC 52 Wisdom saving throw, If the saving throw fails by 15 or more, the creature is instantly die of fear, otherwise it becomes frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, 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 swarm's Frightful Presence for the next 24 hours.

tarrasque Bites. Melee Weapon Attack: +38 to hit, reach 10 ft., one target. Hit: 250 (40d12 + 10) piercing damage, or 125 (20d12 + 10)  piercing damage if the swarm has half of its hit points or fewer, If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the tarrasque can't bite another target.

tarrasque Claws. Melee Weapon Attack: +38 to hit, reach 15ft., one target. Hit: 170 (40d8 + 10) slashing damage, or 85 (20d8 + 10)  slashing damage if the swarm has half of its hit points or fewer.

Horns. Melee Weapon Attack: +38 to hit, reach 10ft., one target. Hit: 210 (40d10 + 10) piercing damage, or 105 (20d10 + 10)  piercing damage if the swarm has half of its hit points or fewer.

tarrasqueTails. Melee Weapon Attack: +38 to hit, reach 20ft., one target. Hit: 130 (40d6 + 10) bludgeoning damage, or 65 (20d6 + 10)  bludgeoning damage if the swarm has half of its hit points or fewer, If the target is a creature, it must succeed on a DC 40 Strength saving throw or be knocked prone.

Swallow. The swarm 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 swarm 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.

kraken Bites. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 23 (3d8 + 10) piercing damage. If the target is a Large or smaller creature grappled by the swarm, that creature 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 swarm, and it takes 42 (12d6) acid damage at the start of each of the kraken's turns.

If the swarm takes 50 damage or more on a single turn from a creature inside it, the swarm must succeed on a DC 25 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 swarm. If the swarm dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 15 feet of movement, exiting prone.

Tentacles. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 100 (30d6 + 10) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. The swarm has hunderd tentacles, each of which can grapple one target.

Flings. all Large or smaller object held or creature grappled by the swarm is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

Lightning Storms. The kraken magically creates three bolts of lightning, each of which can strike a target the swarm can see within 1200 feet of it. A target must make a DC 26 Dexterity saving throw, taking 220 (40d10) lightning damage on a failed save, or half as much damage on a successful one.

 The swarm can take 140 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 swarm regains spent legendary actions at the start of there turn. The swarm’s legendary action options are associated with there five dragon heads (a bite and a breath weapon for each). Once The swarm chooses a legendary action option for one of there heads, they can’t choose another one associated with that head until the start of there next turn.

dragon Bite(Costs 10 Actions).. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 210 (40d10 + 10) slashing damage plus 14 (40d6) acid damage (black dragon head), lightning damage (blue dragon head), poison damage (green dragon head), fire damage (red dragon head), or cold damage (white dragon head).

Black Dragon Head: Acid Breath (Costs 20 Actions). The swarm breathes acid in a 120-foot line that is 10 feet wide. Each creature in that line must make a DC 54 Dexterity saving throw, taking 670 (150d8) acid damage on a failed save, or half as much damage on a successful one.

Blue Dragon Head: Lightning Breath (Costs 20 Actions).The swarm breathes lightning in a 120-foot line that is 10 feet wide. Each creature in that line must make a DC 54 Dexterity saving throw, taking 880 (160d10) lightning damage on a failed save, or half as much damage on a successful one.

Green Dragon Head: Poison Breath (Costs 20 Actions).The swarm breathes poisonous gas in a 90-foot cone. Each creature in that area must make a DC 54 Constitution saving throw, taking 770 (220d6) poison damage on a failed save, or half as much damage on a successful one.

Red Dragon Head: Fire Breath (Costs 20 Actions).Tiamat breathes fire in a 90-foot cone. Each creature in that area must make a DC 27 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

White Dragon Head: Cold Breath (Costs 20 Actions). The swarm breathes an icy blast in a 90-foot cone. Each creature in that area must make a DC 54 Dexterity saving throw, taking 720 (160d8) cold damage on a failed save, or half as much damage on a successful one.

demon Tail (Costs 10 Actions). the swarm makes one demon tail attack.

A Taste of Undeath (Costs 10 Actions). the swarm casts chill touch (17th level).

Creeping Death (Costs 20 Actions). the swarm chooses a point on the ground that they can see within 100 feet of them. A cylinder of swirling necrotic energy 60 feet tall and with a 10-foot radius rises from that point and lasts until the end of swarms next turn. Creatures in that area have vulnerability to necrotic damage.

tentacles Attack or Flings (Costs 10 Actions). The swarm makes ten tentacles attack or uses there Flings.

Lightning Storms (Costs 20 Actions). The storm uses Lightning Storms.

Ink Clouds (Costs 30 Actions). While underwater, the swarm expels an ink cloud in a 600-foot radius. The cloud spreads around corners, and that area is heavily obscured to creatures other than the swarm. Each creature other than the swarm that ends its turn there must succeed on a DC 46 Constitution saving throw, taking 160 (30d10) poison damage on a failed save, or half as much damage on a successful one. A strong current disperses the cloud, which otherwise disappears at the end of the swarm's next turn.

tarrasques claws (Costs 10 Actions). The swarm makes ten tarrasque claws attack or tarrasque tails attack.

Move (Costs 10 Actions). The swarm moves up to half there speed.

Chomp (Costs 20 Actions). The swarm makes ten tarrasque bites attack or uses there Swallow.