Passive protections are often not enough when under direct attack… They are like having a cute sign saying “keep off my lawn”, but not everything respects polite requests. So you must fight fire with fire and attack the thing back.
As above so below.
The first step is to banish it, which is the astral equivalent of throwing it out the door. Then you place wards to lock the door. If it still comes back (many do) hurt it and it will go find easier prey. If it still comes back kill it.
We have a bunch of basic turoriaks here:
https://forum.becomealivinggod.com/t/forum-tutorials-parasite-collection/156295/16