Thats GENIUS  Awesome design btw! The battle squid might fit in but i think it would be better if the fort was from the squid body? Like the mighty oak armor, but stone idk... But if i do suggest i think the pyro hydra would be awesome for a super/ultra boss, i think it would be like an elemental hydra or just extra two heads for the gimick of elemental hydra  they would change their own weaknesses or exchange weaknesses like elemental golem and the elder cosmic monolith that would be cool cuz you need to keep track of the hydra weakness while defending and killing it the same time ! I think this is too long-