Balum Bombarda, the Calamity Cannon

Antimagic Susceptibility. The Cannon is incapacitated while in the area of an antimagic field. If targeted by dispel magic, the armor must succeed on a Constitution saving throw against the caster's spell save DC or become petrified for 1 minute.

Calamity Cannon.  It launches a beam of antimatter through a portal after 10 feet from the end of the barrel.  Anything that touches the beam takes 1,000 radiant damage and knocked prone, with accuracy that will hit anything without having to roll, similar to Magic Missile.  It takes 15 minutes to charge up, and once it is fired, it cannot be fired for another millennium unless manually reloaded by finding an Asthresis Crystal and a barrel of Antimatter, loading the antimatter into the chamber, which was behind the barrel, and put the Asthresis Crystal behind a panel on the top of the back of the barrel.

The Calamity Cannon can take 1 legendary action. Only one legendary action option can be used at a time, and will only gain another legendary action if a millennium has passed , or if manually reloaded by finding an Asthresis Crystal and a barrel of Antimatter, loading the antimatter into the chamber, which was behind the barrel, and put the Asthresis Crystal behind a panel on the top of the back of the barrel.

Calamity Cannon (Costs 1 Actions).  It launches a beam of antimatter through a portal after 10 feet from the end of the barrel.  Anything that touches the beam takes 1,000 radiant damage and knocked prone, with accuracy that will hit anything without having to roll, similar to Magic Missile.  It takes 15 minutes to charge up, and once it is fired, it cannot be fired for another millennium.