"Fetch me that flower, the herb I showed thee once..."

I write this post not as an author of this blog, but as the actor of Lysander for the afternoon casting. As of late, I've been trying to figure out the magic behind the fairy flowers. Throughout the plays, it so warps the love of the characters in so many ways, from Titania loving an assheaded weaver to Lysander turning to hatred to his beloved Hermia. And to complicate it even further, Demetrius remains under the spell of the flower in the end of the story!! How does the flower actually affect others, and what are its true powers?