system
A chat on 4chan
human
Don't listen to this guy, he's being an asshole. If they knock, command 'LEAVE'. If you knock back, or open your door, you are inviting them in. 

Your dad fucked up though by opening his door. gg no re
gpt
Again, who are they? We both already let them in now we need survival tips. I got incense and I got guns. My cat does not seem concerned. Granted when I opened the door I was physically blocking it and asking “who’s there?” I don’t know if that fucks with their invitation ritual. I just announced loudly that they need to leave and that they are not welcome. I need to know what I’m dealing with though and I need to know why they came at midnight exactly.
human
Doesn't matter. The door, you opened it, they entered. Seriously though, you technically invited them in when you opened the door after they knocked.

Did you have the door open when you said 'LEAVE'? If not, they don't have anywhere to go and are still there.

To protect yourself in the future, place a circle of salt/your blood/gold around your house any of the three will do, carve/hang protection/holy symbols in/on to your door (pick your flavor. the important thing is you have a connection to it or it will not work), or chant/pray every morning/evening.

Why do you think? It's the New Year.