There is a bit of a misunderstanding here, obviously.
The little 'beast gates' spell you are talking about is certainly fluff and fantasy or at least associated with it.
Firstly, Vegeance, we need you to tell what you mean by saying 'beast gates'. From only hearing the word 'beast' and 'gates' it gives us a huge clue for association with fantasy movies, you can call it 'fluff'.
There is not 'gate' for physical animals, to begin with, if that's what you're talking about. You want a pet? Buy one in the pet store or find one that is abandoned.
You are talking about the astral? Well, this is certainly junk as well.
Firstly, the astral does not contain and physical gates that 'hides' or 'cages' anything behind it. That's fantasy. People who say such things probably do not understand the astral world and what it means, and certainly not how things are manifested there.
Let me enlighten you for a bit.
Things and objects in the astral are basically manifestation of thoughts and energies. You attract all of the negative or positive energy you have by yourself. The positive energy and thoughts may be manifested by positive entities or deities, and the negative energies and thoughts may be manifested by bad sights, malicious deities or entities.
You basically attract all of the malicious astral beings by your energies, thoughts, feeling (such as fear and being unconfident) which might be what you grant the term 'beast'.
Thus, there are no 'doors' or 'gates' that 'cage' astral beings and entities. You can forget about it and learn about actual astral projection.