I'll tell you colin... this thing he is dealing with, in my personal opinion, is not like a regular paranormal attachment thing as it is thought of. I have only heard of/witnessed this particular kind of situation once before and I am no expert on it by any means. That said, it is clear that he has Walked this 'between' since he was very young. The accident just brought the situation into his forebrain/conscious level more than likely. It is also clear that he has dealt with dark entities for many years, he is aware of that somewhere in his psyche, and it doesn't bother him... He is freely Walking that. The repeating dream/visions are more than likely his Spirit attempting to communicate with his conscious self, push for self-responsibility, and probably warn him of a line he is crossing.
There are other Beings dwelling in many realm's other than the cut and dried, dark or light, demon or angel, ghost or other. The other individual I watched enter into this kind of 'agreement' was dealing with trickster's... Dark tricksters, but real enough Beings, as in not ghosts, demons, angels etc. Where they belonged or came from or how they were able to bend the rules and regulations is anyone's guess. This individual just up and started talking about 'his gang/brothers/crew' whatever one day... and how they had endowed him with higher wisdom's and no small amount of power over others... He told me 'they' had given him authority over 7 - SEVEN -- Soul's to do his bidding and he was very proud of that. I, on the other hand was past shocked and literally sickened. Now, I was very close to this individual so I knew he wasn't lying about what he thought to be true... and I had witnessed first hand some of the 'what evers' that manage to walk in and out of Door's and other... so I took it very seriously. My first response was to try to talk some sense into him. No go. My next response was to appeal to his Light. No go. Next response was Challenge his authority. No go. Last, I challenged 'the crew'. Problem was, they had been freely bonded. So.
In the end, the experience that finally put and end to his allegiance was apparently so horrific that he literally had to leave the area and wandered here and there ever after. I did not want to hear it, nor would I let him to speak it to me. I turned my back and walked away from this dear friend forever. He never came back from that binding. And here is the thing... He knew he was accountable -- for whatever dark deed's they did out there in wherever/whatever realm together. This knowledge crushed him and he was dead not long after.
This is a very good example of the truth of the situation I think. When I first read this sentence last night, I was sure it read "you and the 7 can't hunt here". I could have sworn it. Today, I see that was not what was written. I am assuming there is a correlation but I won't assume to guess what it is. The point is, The Light immediately challenge's his right of Authority. That is the Rule and The Way. That tells me he is bound to darkness despite what, who, or why.
So, I have given you my story and hand to heart it is true. Now, I am going to speak some advice that I held back from last night. Take it or leave it. You need to walk away. I am not The Creator and I am not allowed to judge a man's heart. But, I am allowed my instinct and my instinct tells me you can not help this one. He has no desire to break this bond. Unless he has come to you and ASKED for help, walk away. If he has, send him to those with more experience in these area's
Curiosity can lead you down a very dark path with Tricksters. Be aware, Be safe, Walk in The Light.