You are describing a textbook hag attack, which is the origin of the word nightmare - the “mare” is a parasitic spirit related to incubi that feeds on humans at night, sitting on their chests, choking them and taking their energy.
You can banish like this, but you didn’t kill it so it exists somewhere and come back. Typically, these things prefer not to fight so if you are too difficult they will go in search of easier prey.
Set up wards and shields to protect yourself from attack rather than having to deal with an attack after the fact, and stop the uninvited from entering your space.
You’re also, based on your other thread about to get into some very baneful working - don’t forget like attracts like - doing baneful magick attracts nastier astral entities, so it’s ideal to put protections in place asap. You have some experience with astral combat from this thing, so you can thank it for that, but there’s worse things out there.
If you had one, there’s probably more around and inside you. Like ants or mice - one means there’s usually more. By the way they can also influence you to do bad things because they feed off that negativity, so be sure that all your decisions, especially one that come from a place of pain, are “real” and not their idea.
There’s no definitive zoology for the astral and bullions of types of beings. Some common encounters happen often enough that there’s a general agreement of definitions, but even these change between cultures and over time.
So a “mare” is possibly an incubus/succubus, possibly an imp, or a goblin, or human ghost of a degenerate kind like a Dybbuk. I call them “lesser beings”, they are usually not very verbal, are primitive and cannot be reasoned with. The appearance is fake and designed to scare you because they are eating your fear and want you to make more of it - and anything they can say is always a lie so there’s no point trying to talk to them.
My personal approach sounds harsh but avoids the most issues - kill it. Or try to. As I’ve said many times on here, if you do that, it’s not just between you and it - you are SEEN to be dangerous and not to be messed with. It doesn’t drive away existing attachments but does stop a lot of new ones as a basic part of your defense strategy.
Be the nastiest thing in your local astral and you won’t have any more issues.