Beast of Liberations, Crafted Calamity of the Saurosa.

Walking Building: The construct is immune to all forms of forced movement or teleportation. It cannot have its form altered in any way.

Mechanicus Necessitous: The construct always goes last in the initiative order.

Hard Shell: When the construct is not facing a table, it is resistant to all damage.

 Spellcasting. The construct is a spellcaster. Its spellcasting ability is intelligence (spell save DC 19, +11 to hit with spell attacks). The construct has following spells prepared:
At will: Guiding Bolt, Ice Knife, Magic Missile (5th level)
3/day: Fireball, Lightning Bolt, Dispel Magic
2/day: Synaptic Static, Ice Storm, Sickening Radiance, Cone of Cold
1/day: Gravity Fissure,Chain Lightning, [ spell]Dominate Person[/spell], Fire Storm, Meteor Swarm

Multiattack. The construct makes two Crush attacks and casts a spell it can cast from its spell list.

Crush. Melee Weapon Attack: +14 to hit, reach 60 ft., target all creatures in a 10 foot radius. Hit: 37 (7d8 + 8) bludgeoning damage.

Hubris Denial (1/long rest) [Can only target a target that taunted the boss]: The construct fires a beam of unstable energy at a creature, which explodes the ground at their feet. The target must succeed on a DC 22 dexterity saving throw or take 51 (10d10) fire damage, halved on a save. The construct then fires its Apocalypse Rail Horn at the target.

Platform Weapons

the construct follows a 3 turn cycle. At the end of its turn, the construct switches its active Platform Weapon to the next one in the list, restarting the list after the last one. Platform weapons can be disrupted by a table reaching a damage threshold while the beast is at their table. If a platform weapon is destroyed, it skips it in the cycle. The construct uses its active platform weapon at the start of its turn.

Calamity's Cause: the construct chooses a space it can see within 120 feet. All creatures within a 30 foot radius of the chosen point must succeed a DC 20 dexterity saving throw or take  43 (14d6) fire damage, halved on a save. Creatures who fail by 5 or more are knocked prone. 

Apocalypse Railcannon Horn. Ranged Weapon Attack: +12 to hit, range 600 ft., 1 target. Hit: 95 (15d12 +4) force damage. This attack ignores cover.

Erasure Beam: The remnant beast begins charging a beam attack and a 30 foot wide 500 foot long beam emanating from it begins to glow with elemental power. At the start of its next turn, it unleashes the beam, utterly annihilating anything standing in it. All creatures (besides Kaijus) standing in the area are instantly killed. Creatures killed by the blast disintegrate to dust unless they succeed a DC 25 constitution saving throw.

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

Punch: The construct makes a punch attack

Spellcasting (1/round): The construct casts a spell it can cast from its spell list

Stomp (1/round): All creatures (besides shield cells) within 10 feet of the construct must succeed on a DC 20 strength saving throw or take 29 (5d8 +8) bludgeoning damage, halved on a save.