You have no idea what is in here. It's called "figment of imagination" but that's just as descriptive as cologne names. Your father gave you a massive stockpile of "imagination" that he implores you to use. You try to use it wherever you can, but when you describe it to somebody, "hey look at this imagination." they just go, "what?" as they should. You dislike "imagination" for this very reason, because you have an excess amount of this, and you have no idea what to do with it.
Unfortunately, there aren't a whole lot of spells that call for it, and the ones that do seem like they need a buttload of it, but in reality, they only need a little bit. Fortunately, this spell is one that requires some imagination, and even more than the usual pinch. This spell is quite volatile, so it requires a lot of imagination to keep it grounded in reality.