There’s only so much I can do with this one…, but I’m willing to give it a try. (Perhaps the ‘my brain hurts now’ reaction to dealing with such bad writing will be an adequate distraction from the actual pain I’m feeling in most of my body.)
First, the necessary changes, based on actual rules of grammar, punctuation, etc.:
Unnatural is misspelled.
Change the comma after spread to a period and begin a new sentence.
Delete the comma after cure.
Nevertheless is one word, not three. (It’s also an adverb — eek! *laughs at averb-phobes*)
Change the comma after attack them to a period and begin a new sentence.
Guards is misspelled.
Change their too to they’re too, and change thier already to they’re already.
Add a comma after themselves.
Realising (or realizing) is misspelled.
So that’s all of the corrections made according to rules of writing. I’ll also change bits of it to help the sentences flow better, make a bit more sense, etc. In particular, there’s not realising that they would soon become badass plague doctors. What does that even mean here? *sigh* Because I cannot ask the writer (and am unsure the writer could tell me anyway), I’ll make my best guess and rewrite the end of the sentence accordingly.
In a small village, a plague that could only be described as unnatural and demonic had started to spread. Plague doctors came to create a cure or to take this opportunity to earn some gold. Nevertheless, the sick tried to attack them. The guards couldn’t help the doctors because becaues they were too scared or already sick themselves. the doctors had to find a way to protect themselves, not realising they’d become quite formidable as a result.
As my twin pointed out, the writer of this example has no frakkin’ clue what actual plague doctors did, ’cause it wasn’t treating the sick.