From? It's a gift from someone long gone.
An Outsider in this context is a being from beyond our perception.
The Powers are what you make of them, although there is some guidance within the text.
The main risks emotional and mental. There is the potential for the ritual to bring up uncomfortable memories.
Is this not horrendously unsafe to give over someone else's body, recklessly endangering them, to another entity who is also messing around with memories? Not to mention no protections or wards in place to prevent the Outsider from running off? I see you replied to someone else saying "The main risks emotional and mental. There is the potential for the ritual to bring up uncomfortable memories." What about these dangers?
The Vessel has the power to withdraw themselves from the ritual.
If you withdraw yourself from the ritual it ends.
The Outsiders drawn by this ritual have no interest in the physical world, their only interest is in learning more about you. Where would they run off too? If they will the Vessel to leave the circle than the ritual is broken and the Outsider returns to their home.
I do not understand how you got the idea that you "give over some else's body" the Binder and the Vessels are collaborators in this ritual. If you are forcing someone to do the ritual with you, than you are the danger and you are undeserving of power.