To those who much prefer Mr. Hyde over Dr. Jekyll: Don't worry, he won't be gone for long! He's just switching things up a bit. During this and the previous chapter he's been pretty limited to the role of "two dimensional guy who harasses Jekyll and makes judgy commentary about the goings-on." The next time we see him he will be doing something quite different. It will also be really hard to draw.
In an earlier draft, Jekyll added valerian root to Frankenstein's potion, but no real, over-the-counter sleep aid works as fast as shown here, so I decided to go Full Witchy on this one. I'm not sure if ancient alchemists ever tried to use this particular crystal, but they probably tried to feed people rocks at some point. I mean, people still try to drink silver, so.