I'm honestly curious as to what his reaction would be. What do you guys think?
I just read through the article about the Dark Arts only to find something surprising. It is stated that the "Laughing Potion" is effective against the deadly cry of a Banshee. WHy is that? Why would a potion that seems to induce laughter have any effect on a Banshee? Well one could argue that a laughter inducing potion, if forcebly given to a Banshee, could keep her from emitting their deathly shreek. But is that all that is to it? And why would you mention it in a Book of Potions when it'd be pretty hard to force a Banshee to drink anything at all before she can screech? The answer is simple: There has to be something else that the potion does. It has to affect the one who seeks protection from a Banshee and not the Banshee itself. This notion is only encouraged when you look at other potions. There is already a Laugh-inducing Potion which means that the Laughing Potion must have different ingredients than the Laugh-inducing Potion and therefore a different effect. But what might that effect be? Banshee's are considered to be spirits, if not amortal like Dementors. So that means that most basic effects won't affect them at all. You can't kill/hurt something that isn't alive or maybe never even was alive, right? Than what might affect a creature like that?
Why don't we look at similiar creatures to the Banshee. In the article to this creature it is said that they have similiarities to the Dementors. We know that the only thing that has any (significant) effect on a Dementor is the Patronus Charm. A Charm that utilises the caster's happiness to create a magical force which can ward off many different Dark Creatures, including Lethifolds.
And since we're talking about the amortal being that is a Dementor, why not look at other non-beings. The first that comes to mind is, of course, the Boggart which, once again, has a very particular way that leads to it's defeat: The usage of the Boggart-Banashing Spell. This spell forces the Boggart to take a new, laughter inducing form which then leads to it's defeat/destruction when it is laughed at.
And now to the last known non-being: the Poltergeist. This apparition is a little different than the other two or even a Banshee, if she really can be considered to be something like that. They can't defeated. They may not be as troublesome as the other non-beings, but it is the only one that has no known way of being defeated or warded off. Just ask FIlch who tried everything he could for years to get rid of Peeves. But they just suddenly come to be when a place inhabits many adolescents. Adolescents who share laughter with each other, pull pranks and generally are more relaxed than adults would be. So what of this triggers the creation of a Poltergeist, a chaos loving apparition? I think that it, like the other amortal non-beings, is created by a specific emotion: Mischief. While the Dementor is born out of despair/depression and the Boggart out of Fear itself is the Poltergeist just made of the mischief that the children cause. That is probably why they are immune to the general weakness of non-beings. They aren't born of a particular dark emotion, but rather a trouble-making one which itself induces laughter. So it might be that a Poltergeist would be vulnerable to sadness or the lack of freedom to be mischievous.
So how does all this have anything to do with Banshees and their weakness against the Laughter potion? Easy, they just might be amortal non-beings, too because of said weakness. The question would be which emotion causes their creation? Their history of emitting their screech when someone if about to die or the moment someone died might suggest that they were born out of the sadness caused by the loss of a loved one. But why would their wail be deathly when that was the case? Let's look at the effect other amortal non-beings have and what they are created from. A Dementor, created by despair, sucks out the happiness out of you to create even more despair. A Boggart, created by fear, turns into your worst fear to unduce even more fear (Gosh that was way too many "fear"s in one sentence). And a Poltergeist, created by Mischief, love to cause even more chaos. So every amortal non-being induces the emotion that created them into closeby people. Seems awfully fitting for the Banshee as well, right? Born out of the sadness of a tragic death only to bring more sadness by causing more deaths. That would also make Banshees the most dangerous known amortal non-being since their wail causes death to everyone around it. Not even the most dangerous non-being, the Dementor, can compare to that. A Dementor has to come close enough to perform their kiss while a Banshee has a far wider range in which they can kill everything immidiately.
That would, of course explain their weakness against the Laughing Potion. Because what is more harmful to sadness than laughter and happiness. So it might be that the potion doesn't only induce laughter, but rather induces happiness and a general nice feeling in the drinker which can ward of the negativity of a Banshee.
Let me know what you thought about this theory and if I've got anything wrong or if there are points which I might have missed.