Have you tried talking to it? In the Internal Family System model, you have wounded or exiled parts, and "managers" that protect those parts. Generally in unhelpful ways. Like they protect a wounded child part by never letting you make any art ever, so it can't get criticised for it. Or by drinking copiously, so it doesn't have to feel anything painful.
These parts often spontaneously appear as psychosomatic visualised sensation. I have a spiky star at my heart centre, a rolladoor that slams down on the right side of it, stuff like that. I didn't come up with these as metaphors, they just appeared when the therapist asked me to drop in and listen
I'll call it the Octopus for now because we don't know if it's a Part of you or not
You are aiming to sit beside the Octopus, not get involved with it, and for the time being you are not expecting anything from it
So you would get quiet and connect to the sensation and image of the Octopus. You would say (truthfully, for now), "Can I talk to you for a bit? I promise I won't try and get rid of you, I won't judge you or shame you or tell you to shut up, I just want to get to know you"
You might place your hand gently over where the octopus is.
Then you ask questions, and wait for thoughts to spontaneously arise in response. Make sure to give a good long wait after each question. There's often a "this is dumb, nothing's happening" phase and then the answer suddenly appears.
Questions include:
- What is your job? (Even if it's not a Part, it still probably has a reason to be here, so you can ask it this)
- What are you here to do?
- Do you like doing your job?
- Are you protecting me from something?
- What are you afraid might happen if you stop doing your job?
- Are you happy, living here in my chest?
- How long have you been here? How long have you been doing this job?
- How old do you think I am? (Sometimes parts don't realise there's an adult around, they think responsibility for the whole person rests on their shoulders alone)
You should reassure it throughout. If it thinks it's protecting you, you express appreciation for that even if it's really bad at its job. Even if it's a demon or etc, right now, you're in peace negotiations. Keep your word that you're not going to try and kick it out in this conversation
Sometimes you can't have this conversation because a different part will step in and block it. In that case, you have to gently ask this new part if it minds stepping aside just for a few minutes so you can talk to the Octopus.
When you finish, thank it for talking with you.
At this point hopefully you should know a bit more about what it is - if it's a part of you, or something external. If it's a Part, you can google for more about IFS processes.
It's been there a long time, so I'm inclined to think it's not hostile, because it could have done worse to you. It might, however, be counterproductive. Potentially you might be able to give it a new job that would be more helpful to you.