I also see a black dog from time to time, on first site I also was wary and since I was in circle in ritual, I knew that I was supposed to take control, so I put out a strong energy to claim my circle as you would your own room, then it came and sat beside me and seemed to be watching the events.
I have no idea if I should have banished it but although it was a little unnerving, it did seem to be for me rather than against me, so I let it be.
However, I have had other visits from dogs, one was unwell and was looking for some gentle energy it seems and one was snarling and clearly unfriendly.
If you are obviously and without any doubt that you are in trouble, act immediately and gather your most confident and strongest energies and mind set and let it know you are 'god' and that it cannot win you over. If it was sent by another practitioner, then it will return, but remain calm and deal with it, firmly! You may have to keep doing that each time it reappears. Some things have a limited life span and they will just never come back.
If you keep getting the appearance and you are sure its unfriendly, be prepared for it to come under other guises too.
I don't want to worry you, just giving you prior warning, these things in reality, are actually very rare.
As Bym says, investigate Anubis too (IMG:
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Hope this helps.