The leviathan looks like a 5m long, fat, dark cyan ender dragon with thick legs. It has long horns, large eyes on the side of the head, and a fish's tail fin. It is hostile, and spawns in water. It can touch blocks, and normally walks. It cannot fly, but can glide. It breathes water, and will 'drown' if kept away from it for to long. It can breathe a cone of fire, which removes rain. They cannot move through air without rain in it (rain-free air is treated like a solid block), but also cannot jump on it, and move on it as fast as they would falling. They are very fast in water, but half the speed of the player on land. They have high attack and defence, and will chase the palayer anywhere, until they run out of oxygen, when they will run at twice the player's speed to the nearest source of water. When they go fast on land, they are harmless. They drop leviathan scales, which can be made into humidifiers and dehydrators. They are made with a 'helmet' shape of leviathan scales, 3 redstone on the bottom row, and a bucket with either nothing or water. They create a sphere of rain or no rain with radius equal to the amount of power inputted.
This... honestly seems really really cool. I would love all of this stuff, the humidifiers would be great for building sprinkler systems and other stuff, the leviathan seems like a really neat boss, and I especially love its ability to swim through rain. Full Support