>Would it be possible for us to encase the demon in a dimentionally seperate prison, one that only we and those we choose can enter and exit? And if so, would it be possible for us to tie the imprisonment to the demon's mind in such a way that the demon would be released if it genuinely changed? And if so, could this be done beyond any ability for the demon to trick it into falsely determining that such a change has occurred?
>In short: Yes.
>In order to imprison the demon in a dimension separate from this one, you would need to conceptualize and visualize somewhere to put it. A jail, an old race track, a love hotel, a closet, some form of enclosed space. If you do not, it could end up anywhere, including NOWHERE, so you need to put it SOMEWHERE. The thought of imprisoning a being, even an evil one, in some kind of endless black void is one you don't care to embrace, even if it's only temporary.
>Keying this seal to the demons own mindset is also possible, and you believe it would be impossible for it to deceive the seal you create. Sincerity and honesty are part of the core of your being, as much as your kindness, and your power reflects this. Any seal you create should only respond to sincerity and honesty, in kind. In setting this condition, this would also ensure the safety of your access, as well. If the demon's only method of 'escape' is through genuine reflection and atonement, it shouldn't be able to take advantage of the 'door' you'd be leaving yourself.
>If you wished to enter this prison yourself, you would need a 'key'. An object to connect to the demon's jail, a touchstone between this world and its dimensional prison. Ideally, this would be something connected to your prisoner's nature; in this case, the demon obviously has an affinity for water, and is a scaled reptile of sorts, so a vial or jar of water from the pool behind you would do nicely. All you would need is a container to put it in. It would also be possible create this key later.
>While the ability to do this you do possess, it is an order of magnitude beyond anything you've attempted so far. The energy required to create this seal would be large and, fatigued as you are, you don't think you alone would have enough energy to guarantee a successful seal. You will need to cooperate with at least one, possibly both, of your fellow Magical Girls, pool your energies, in order to ensure success.