Hi. I belive the only way to get a familiar is to ask Satan or the Gods for one, before you get a pet, because they will have to be a special soul.
The way I got mine, when I was still a child, and freshly dedicated of a few months, I was sitting in my bed at night, after a meditation session, and talked to Satan directly.
I told Him, that I want a pitbull/amstaff, even if they are considered an aggressive race, because they are most loving and would give up their life to their human, they love the most passionately, and are very protective.
I also made sure to tell Him the reason why I want a dog. To help me get through the traumas that I was going through with my parents at the time, so I could go outside more, and as I advance to help me with my magick, be next to me during rituals, help me practice the merging astral conscious and many other.
These were things that I personally planned, but you might have other goals with your familiar and other reasons to get one. Make sure there is a reason you ask for a familiar, and make sure you point it out when you ask for one. A familiar is a huge responsibility not only physically but spiritually as well.
The same night I spent visualizing my life with that dog, even it's fur color, the feeling going with him for a walk, bathing that big muscular boy, feeding him. And sure enough after a few weeks, I had this puppy in my room the exact same race, same color I had visualized, which turned out to look exactly as I visualized when he grew old.
I thank the Gods and especially Satan immensely for this gift. This familiar has helped me manage an ongoing trauma, and even heal some of it when it was over. During my whole teenage years, he even sat next to me when I was doing rituals. He would willingly come and sit as soon as I lit the candles for rituals, as if he just knew. Even helped me practice the merging astral consciousness and many more.
So everything I told Satan I planned for my journey with a familiar, I did accomplish. It is important to be a man/woman of word when asking something from the Gods.
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Now, something which wasn't talked about much when it comes to them is that, Satan and the Gods can take away this title of a familiar from your pet.
I talk about this because it has happened to me, and They can decide this for several reasons. You're either not taking care of it properly, or you're about to be separated and the connection will hurt both of you; or other reasons that the Gods decide depending on specific circumstances.
For me it was the separation, the period prior going to college, I didn't know I was about to go, but I felt our connection was different.
This dog when I was gone would sit next to the door, and would not even be able to drink water, despite how hot the weather was. Would literally die waiting for me. But a few months before going to college we started to not be as inseparable as before.
And it is a good thing. This dog has served me well in my journey. Thought me patience, thought me kindness, helped me with my spiritual practices. And I am grateful I have him in my life, and I am grateful he is happy. I still see him from time to time, and I'm still the person he loves the most. But now the separation does not cause harm in any of us.
It's important to note, a familiar is not a simple pet. Think deeply about it before asking for one, as this is a very important decision. You will see they also have spiritual needs on top of physical ones. Same way he would come with his food bowl to you to feed him, he would come to you when you're cleaning your aura and sit on your lap to clean his aura as well. So you're not only putting in the work to meditate for yourself, but for your familiar as well. And remember that the title of a familiar can be taken away from your pet if the Gods decide so. Therefore you have to make sure you take proper care of it.
There aren't certain types of animals that are better. I would say, if you choose to ask for one, make sure you have a good reason for choosing that type, that you somehow feel close to that type of animal, not just because "it looks cool" or other reasons that are not logically beneficial to you.
Hope I helped.
Hail Satan!!
