A polished silver vial with a crescent moon etched into it

Your eye is caught by the gleam of silver, and you pick up the vial which is about the size of your finger. A wooden stopper seals the end, and a symbol of a crescent moon decorates the tube.

You consult your Uncle's book, and find that it seems be something called "Lupus Essentia". Compared to some of the other vials, there seems to be quite extensive information about what the Lupus Essentia is and does.

Thys potion containeth the vital qualyties of the wolfe. Used Sparyngly yt confers graet swyftness & much improved hearyng and smelle upon the user. Excessyve usage hath been lynked to the affliction of lycanthropy, whych the common man know as Werewolves.

You read in archaic English. That explains the lunar symbolism, and the silver vial then, you think. You should probably be careful with this one.