Yes it`s possible but its considered a form of darkest magick out there for a bloody good reason.
So there is no one who knows how to do it out there that would be crazy and/or stupid enough to actually teach it to you, not to mention that I hope you are not crazy/stupid enough to try and figure this one out.
"So there is no one who knows how to do it out there"
If no one knows how to do it, then it doesn't exist. If you're looking to take someone's soul, you're out of luck. There are other things, like binding a spirit to an object, or something related. A spirit itself has its own consciousness, so that would be the only way I'd know how to "trap a soul".
In theory, a process to unwillingly trap one would be hard, but if one agreed to having their soul used by another, it could be possible. I am not sure why you would want to ever give a person or entity your soul though...
It is mostly done through deals made with the spirits and tricking them. Never ends well.
For example in goetia there is the summoning circle which the witch is inside and the triangle that teaps the demon. With proper rites the demon can't leave until you break the circle and in order for them to get freedom they have to make a deal and the rest lies in phrasing.
i have heard of binding a spirit to an item or something as a way to trap them [like a bad curse] but you can't catch peoples souls like fireflies, especially if the person is alive right now.
Re: The capture of souls By: WhiteRav3n / Knowledgeable
Post # 11 Jun 16, 2015
It isn't possible to steal someone's entire soul, but in some traditions, there is a belief in soul loss via thievery where a "piece" of the spirit attaches to the taker due to emotional attachment or "runs away", retreating to a place of safety due to trauma. No one looks kindly upon those who purposely take, and you're liable to meet serious aggression if another magick practitioner gets involved to retrieve the soul loss.
Soul loss symptoms can include nightmares and dreams of the "taker", depression, and PTSD symptoms.
In significant romantic relationships, soul loss can be mutual if the two have symbolically "given" apart of themselves to each other or pledged/promised such things sincerely like so many stupidly do. Especially if one is not desiring separation it can cause serious mental disturbances for both parties involved.
But the consciousness is a different "part" of the soul, commonly referred to as "the mind", and that ties deeply with the personality or identity and cannot be stolen.