Even still, it seems appropriate to talk in further detail. That said, to start, this is the email I sent to the individual in question:
Well, what we experience when going through and working with the benevolent and wrathful sides of ourselves is intensely personal. So too is this the case when we work to unite and reconcile the two. Some experience delusions of grandeur, extreme despair and depression, suicidal episodes, loss of jobs, friends abandoning them, or being cast out of their homes. Others simply experience strong, unexpected shifts from being lucky to extremely unlucky. I experienced radical changes in how I viewed people, things, locations, etc. and it changed how I interact with people.
Sometimes the changes are genuinely good, and other times the things that are competitively good to what could have happened are really just mixed blessings. I've seen folks attempt the work and become psychic, later losing themselves because they couldn't learn to control their abilities. I've seen folks become permanently haunted, as they've turned themselves into spirit magnets.
The reality of it all is almost deceptively simple: you're working to become a God when you do this, and spirits don't usually like competition.
You're looking to effectively combine Fire and Ice and learn to make something from it. This is no small feat. Its a hell of a lot like going for a magical Big Bang....and of course, work like that is going to attract attention; some of it'll be good, some of it'll be bad, but rest assured, if you want to make some waves, that's one way to get that done. This isn't just some casual, simple, clean cut line of work that you can light a candle for and be done with...that's not the way this works.
When you do start down this path, you're in it for the long haul. There aren't any oaths to consider, really, or even any pacts, save for the one that you are making with yourself. If you get stopped up and scared, you're going to be fucked until you decide to make a change and either regress or push through.
There are very real dangers of delusion and the use of magical workings that will befuddle you and cause you to do stupid things. You're going to be setting the wheels of fate in motion, and you can't just exclaim "stop the world, I wanna get off!" and be done...it doesn't work like that.
Even still, the rewards are crazy, unthinkable, and sometimes downright strange in a happy sort of way. Serendipitous events occur like crazy, you can start getting some really interesting and quickly-manifesting results, and you will look at things differently. You're not going to be seeing the world with the same eyes anymore, but that is a blessing and a curse.
You're not going to be the same old [insert your name here] anymore. Your relationships will change, and you will be put on a different path. This isn't something for the faint of heart, so if this is something you're drawn towards, proceed carefully. If the burden gets to be too much, you will need outside help to get you back up on your own two feet, but even then, it'll be a matter of things being your responsibility. You can't be the king or queen of your domain and expect autonomy from the servants, and this gets to be strikingly true when you're managing the denizens of both heaven and hell.
Best of luck.