Dr. Jekyll's Serums

"A serum I created, designed to separate the good from the evil in someone."

- Dr. Jekyll

Dr. Jekyll's Serum is an item featured on ABC's Once Upon a Time. It first appears in the twenty-second episode of the fifth season.

Dr. Jekyll's Serum is based on the item of the same name from Strange Case of Dr Jekyll and Mr Hyde.

Effects

 * The original version of the serum was used to turn someone into their evil self. The latter can take the appearance of the person it is applied to, or it can take an entirely different appearance, depending on how they see their inner darkness.
 * An improved version of the serum was developed by adding a purple flower extract to the original substance, and it separates the personification of inner darkness from their body instead of transforming them.
 * In both cases, the evil self receives a body with extraordinary physical abilities.
 * Mr. Hyde is much more stronger than a normal human, and appears to be invulnerable to most forms of magic.
 * The Evil Queen is able to live heartless, and without having an existing heart.
 * The serum appears to manifest the dark personality with physical abilities respective to the original person's possible views about their dark selves (i.e. Regina views the Evil Queen as heartless, and thus she can literally exist without a heart).