15Helped Create The Marauders Map To Help His Friend Endure His Werewolf Transformations
Even though it's safe to say that the Marauders (James Potter, Sirius Black, Remus Lupin, and Peter Pettigrew) took advantage of their magical map of Hogwarts, the map was created for a reason. Its purpose, aside from helping them sneak around at their leisure, was specifically to help Lupin
anytime there happened to be a full moon. Being a werewolf, self-control wasn't exactly his forte, so his friends put their heads together to create a means for momentary escape.
In their eyes, the Shrieking Shack seemed to be the best hideout for Lupin to lose himself in anytime his lycanthropic tendencies took over, so they went right ahead and used some magical parchment to give him a leg-up on his curse. Seeing as they couldn't do much to affect the actual beast within, they did their best to, at the very least, cage the beast itself.
After all, werewolf or otherwise, what are friends for?