After you dedicate to Satan you are assigned a Guardian Demon. How quickly you know who they depends on how open you are. What kind of people are you compatible with as a whole? what elements and personality traits are they dominant in? If you see a pattern, chances are your Guardian could have these as well. If there is a past life bond a deep fascination and intense feeling of love can occur immediately upon learning any information about a certain Demon. Your guardian will choose you of their own accord, not the other way around.