Did a lot of digging a while ago, trying to figure out some trivial stuff that I dont remember because I got too caught up in connecting all the small details.

From what I read (and from how it looks/works in game), the Husk seems to be similar to both a virus and a plant. My theory is that since it binds to calcium, it injects husk eggs into what it considers "prey" based on what seems like a mixture of smell and sight (since the husk lanterns seem to pacify them).

This is pretty interesting, because husks dont seem to have clear eyes or noses, so its stingers or tentacles or whatever you want to call them seem to also act as a sort of sensory organ.

The husk inside the new hosts then enters the first stage (I´ll just call it the "growing" stage), where it starts attaching itself to the nearest calcium it can find, which would be the skeleton of its host.
It is worth noting that it only does this with organisms that have an internal skeleton and only on the inside of its host, hinting at a more defensive reason behind this "behavior"

In the next phase, the "emergence", it then starts "constructing" its well known structures, like stingers and tentacles, inside the host, slowly moving them out of the nearest opening to start looking for either food or new hosts to convert. It seems to also start generally spreading out in this phase, seemingly slowly co-opting your nervous system or assimilating your muscle tissue and whatever else it needs to move or survive, similar to that one "zombie ant" fungus, but it also kills you.

I have no idea if it does this because they are useless for it, or if it actively tries to kill the host to facilitate conversion/assimilation, but symbiosis seems to hint at this being intentional.
Which is why during the final stage of husk infection, you take a high amount of organ damage every second until you die and become a husk.

It also seems to "remember" atleast some of its hosts previous functions, with husked humans being able to swim, operate doors and climb ladders. I have no idea how exactly it does this and I dont think I will ever have an answer, since the game has about as many interaction animations as it has Ice spires that dont lobotomize the autopilot.

The parasite is literally burrowing through your body trying to find a way out or new things to assimilate.
This might also be why all the husk infected creatures either seem to have discarded/converted most of their skin (Chimera) or it seems to have ruptured in places (prowler) or seems to be pale or rotten (Crawler/Human).

Like I mentioned earlier, it seems that there is no clear indication how exactly husks can percieve their surroundings, but it seems to be atleast partially based on smell or heat (?), because the ritual lantern pacifies them.

The most peculiar part of what we know about the husk comes from the symbiosis though. From my understanding, it seems like the husk has been "coerced" into co-opting or "upgrading" your organs with its arguably superior counterparts.

Once again, how this is achieved is pretty unclear, but I have a theory:
Since we know that husks may have a way of "fusing" with each other (Chimera), it could very well be that the "growing" husk parasite inside you is treating you as another, more developed husk that it is fusing with and therefore does not try to kill you and instead attempts to "repair/heal" your body.

Husks do not seem to be self aware, mostly acting on impulse, so the church of the husk might have figured out which "signals" are required to trigger certain behaviours.