Xenoqueen Tarrasque

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

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

Reflective Hide. Any time the Xenoqueen 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 Xenoqueen Tarrasque is unaffected. On a 6, the Xenoqueen Tarrasque is unaffected, and the effect is reflected back at the caster as though it originated from the Xenoqueen Tarrasque, turning the caster into the target.

Siege Monster. The Xenoqueen Tarrasque deals double damage to objects and structures.

Double-Bite. The Xenoqueen Tarrasque has an internal piston like tongue, with an extra set of jaws on it. This drastically increases it's bite power.

Acidic Blood. The Xenoqueen Tarrasque has acidic blood. Any creature within 5 feet of it that lands a melee attack must make a DC 20 Dexterity saving throw or take 6d6 Acid. 

Natural Climber. The Xenoqueen Tarrasque can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack. The Xenoqueen Tarrasque 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.

Double-Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 63 (8d12 + 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 Xenoqueen Tarrasque can’t bite another target.

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 Xenoqueen Tarrasque 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 Xenoqueen 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 Xenoqueen Tarrasque Frightful Presence for the next 24 hours.

Implantation. While a creature is grappled by the Xenoqueen Tarrasque's bite, it will attempt to implant a xeno-egg inside the creature. A creature must make DC 18 Constitution saving throw. Upon failure they are implanted with a Xenosaurus Rex or a Xenoraptor egg (Maximum 1). Upon success the creature is not implanted, and is released from the grapple. The egg hatches while inside of the creatures stomach within 1d10 days, the baby then bursts from inside of you, reducing your hit points to 0 and you fail all death saving throws. Roll 1d20, on a roll of 18-20 the egg hatched will be a Xenosaurus Rex, all other resulting rolls will hatch a Xenoraptor. This effect can only be stopped by the Wish spell, or Greater Restoration. (Recharge 5-6)

Acid Spit. As a reaction, when the Xenoqueen Tarrasque is the target for a melee, ranged, or spell attack, it can spit some of it's acidic bodily fluid. The triggering creature must make a DC 18 Dexterity saving throw or take 8d6 Acid damage.  The creature takes an additional 1d6 Acid damage at the start of each of it's turns until it succeeds a DC 18 Constitution saving throw, or doffs the equipment that was struck. Furthermore, the spit will cling to any surface covering a 5 foot area, if a creature enters this spit it must make a DC 18 Constitution saving throw or take 3d6 Acid damage.  After 3 rounds the acid will corrode the surface it is stuck to making it difficult terrain. (Recharge 3 rounds). 

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

Attack. The Xenoqueen Tarrasque makes one claw attack or tail attack.

Chomp (Costs 2 Actions). The Xenoqueen Tarrasque makes one bite attack. If there is a creature already grappled by the bite attack, the Xenoqueen Tarrasque will instead use implantation.

Hive Mind: Call to Action (Once per Day). The Xenoqueen Tarrasque will use her hivemind communication to summon 1d6 Xenoraptors. Also, roll 1d20, on a roll of 18-20 the Xenoqueen Tarrasque summons 1 Xenosaurus Rex.