for the enemies I proposed.
like I said, they are essentially alien plants.
Corneation: the most common kind could be a large eye-like flower at the end of a stalk, this one would have the man eater AI, and shoot yellow lasers at you.
Novillium: an enemy that acts like the antlion, but instead of sand, it shoots volatile arching fireballs that act like molotovs, appearance wise, it would be a large bulb.
the last one is a flying enemy, it doesn't really directly attack the player, but it releases spores that when they come in contact with a block, will spawn Corneations on the block it came in contact with. the spores will be called "parasights"... I can't think of a name for it yet.
I'll leave stats up to you, because I'm not sure what point in hard mode you would want these enemies balanced for. (although I would personally make them post plantera, or post mech)