Star-Spawn

These hostile mobs look like dark green squids with wings and red eyes. They spawn in deep ocean biomes and in The End dimension. They can live outside of the water but they rather be in the water. They attack by spitting a green projectile that inflicts a random debuff or status effect, but they don't just sit back and pelt enemies with their projectile. As they shoot their projectile they will close in on their foe to deliver a nasty bite that does 12 damage. They would have 20 health. Star-spawn are enemies with guardians so if they come face to face, the two would fight. 

Despite their wings, they're rather vestigial, so they don't fly but hover a block above ground. They also fall slowly, making them immune to fall damage like chickens. In water they move faster than they do on land. On death they drop a random potion and a slim chance to drop a chorus fruit, a reminder of their original home, The End. Perhaps star-spawn will spawn more often around ocean monuments and landmarks like End Cities in The End dimension. 

Maybe if a normal squid or glow squid is struck by lightning it can turn into a star-spawn. 

This concept is very much from Lovecraftian literature, so it could have more spooky aspects attached to it.