Other Side Effects of the Putrid Serum

Options

So in the Hallowed Blight Event, the Entity has to get rid of the blight through flowers which excretes a foul nectar. This nectar can then be distilled into what is called "Putrid Serum." I can already see that the stuff mutates the killers, but how?

It has varying effects on different killers: Wraith turns into a hollow tree monster (forgot the actual name of the creature), Huntress mutates halfway into a were-rabbit, Hillbilly... well he's largely the same, Trapper gets even bigger spikes in his back and Doctor gains more eyes but loses his intestines.

What determines these different symptoms and what other side effects are there? I'm guessing that they get stronger, become more savage and/or become addicted to the serum. That's another thing too, does the serum wear off once the event is over and causes the killers to return to normal?

I'm not asking for spoilers, but if any devs do read this, it would mean a lot to have some pointers on what this serum does appart from make the killers scarier than they already were. It's also a good topic to talk about, since it's really interesting to talk about.