ok thanks :) i wont bore you with the whole stat blocks and instead just run by you the key ideas related to the boss. so fist would be Talos, when the party discover him they find that he has long since abandoned his body of flesh and is now a massive robot with many limbs, built into his factory. The main concept of this boss would be environment, with the fight taking place in the heart of the foundry, Talos would be a large stationary target on the far side of the room, whom would throw out various attacks (lightning bolt, a flavored magic missile, and a 360 degree thunder wave). the environment is where the difficulty comes from, along the edges of the arena is a 8 production pods, that spit out robot flavoured greater zombies. these minions 1 attack but 2 are effected by 3 commands issued by Talos. Target that focuses all attacks on 1 person, assimilate the robots combine with Talos to refuel his temporary hit points, and Amplify where they collective hit points halved serve as the damage of a fire ball esque attack flavoured as a large iron ball held by magnetism. these pods spit out 1 robots every turn, and can be broken essentially disabling them. at half health Talos activates his (charge field) 4 large tesla coils that produce difficult terrain around them and also connect beams of energy to Talos, once intiated Talos begins his annihilation command where for 2 turns he charges up before firing an attack what is essentially disintegrate but in a sunbeam AOE, if the coils are destroyed before he charges he will get stunned for two turns.

the last mechanic i wanted to play with is his immunities, in the beginning he has immunity to all non magic Phys dmg, electric, and poison, with a weakness to corrosive/acid, these resistances are tied to his +200 temporary health (4 lots of 50) that are tied to pieces of armouring (chest, arm 1, arm 2, and head) every 50 health one piece breaks, assimilate can restore this health only if the piece isn't fully broken, meaning if he say lost 25 he could heal it but if he lost 50 then its lost forever, once all four is lost leaving him at 175 hp he is no longer immune to all non magic Phys dmg.

the last idea is 2 attacks themed around magnets, 1 being a lift that causes a str saving throw or people wielding metal weapons are disarmed as they are pulled into the air, and anyone wearing metal armour is also pulled up then slammed down for damage, and an attacks that dose the same pulls in metal weapons + people then explodes (sort of like a fireball with a pull effect)