After posting Protecting Medieval Villagers From Droppers, I realized that Droppers must be kept in check-hard in check.
Now, thanks to Classes, a Dropper's speed and agility can pretty easily be overcome-a Level 125 Ranger or Sharpshooter alone should be able to do the trick. However, their sheer numbers and voraciousness, plus their acid attacks, makes it clear they need predators to keep them in check. Nature is on my side here, since like salties (saltwater crocodiles) Droppers are basically unstoppable as adults but are vulnerable to predators as juveniles.
The question is, what predators? Droppers fly at 30 mph, they can fly in any direction (having the agility of a dragonfly), they have squirrel-like processing speed, they can spit powerful acid (albeit from their jaws, which are on the bottom of their bodies) and their many eyes leave them with almost no blind spots. Oh, and they have 1/2 inch thick shells of enamel since they're eggs the size of an elephant bird's (egg, that is).
The good news is, a Dropper is basically a Chomper with wings, so what works for Chompers could quite likely work for Droppers. Droppers also have the following weaknesses:
Vertical Dependence-While Droppers are capable of flying horizontally, and therefore attacking prey from that angle, they really don't. First up, while the eyes on their jaws (which allow them to 'divenom' effectively) technically allow them to fly mouth first, they seem to have a pathological preference for vertical attacks, specifically diving or spitting straight down. (This may not be feasible from an evolutionary standpoint, since there is no real disadvantage to flying horizontally or diving at their target like a regular bird when the circumstances are right and with raven-level intelligence, Droppers should be able to figure out when that is.)
Sleep-Droppers need to sleep, and they don't float when doing that. They hide in high-up and hard-to-access places, like the crooks of branches and knotholes or the eaves of buildings, or else float on bodies of (relatively still) water like lakes or the sea. However, an agile predator could not only get to them but take advantage of their third weakness...
Eyes-Dropper eyes are always open, albeit covered by a layer of protective gel. I feel birds, ferrets, and even some insects could take out or eat into the eyes to get to its gelatinous innards, so this is definitely an exploitable vulnerability.
Now, I haven't even started with a Dropper's Enchantment, Levitation, which takes Newton's 3rd Law and applies it to gravity. Basically, a Levitating creature is pushing against gravity like it would the ground, standing and even running on it like an invisible floor. The natural height of this flotation is directly proportional to the creature's weight-a Levitating human will "stand" six feet above the ground, so if the creature is heavier than a human, they will "stand" lower, while a creature lighter than a human will "stand" higher.
This flotation works against whatever support is underneath the creature, so a bird in a tree will be "standing" above a tree branch. It also varies depending on how hard a creature is "pushing" against gravity, so a creature can "let go" and walk as normal if they want to. I also didn't mention Calcification; any creature that kills a Dropper will get Levitation, but if they eat a Dropper, they'll get Calcified as well. This makes insects seem a good option (since Calcification really shouldn't adversely affect them), but considering a Dropper's size, I doubt they can be a reliable predator.
So, my question is, What Would Serve As The Best Dropper Predator?
Specifications For Best Answer:
The best answer will analyze a Dropper's weaknesses, strengths, and abilities and determine what traits their ideal (AKA "best") predator would need to have in order to succeed.
The best answer will take the information in #1 and determine what predators (IRL or otherwise) would fit the bill. Other potential predators include Plops, Snappers, [Spikagi], Whackagi, and Anklebiters (described here), perhaps even Chompers or Torchblow!
Thank you for your help, this has been a perplexing problem of mine (since I haven't really thought of flying monsters for my story).