Memory Palaces

Ever since I first read of these I've been fascinated by them.  If you aren't familiar, the story goes that Simonides of Creos was at a banquet and happened to step outside just before the roof collapsed.  He realized he could remember who was at the banquet and which body belonged to which person based on their location around the banquet table.  This became known as the method of loci, a way to memorize a great amount of information by relating each bit to imagined locations in our minds.  Later, it became quite a fad, with the locations known as memory palaces.

What if you could access someone's memory palace?  Find the magical phrase, use the proper ritual and you are transported to a structure.  Each room might have odd objects, texts, and maps that the creator wished to remember.  It might be a kind of mini-plane the players are actually transported to, or more an ethereal dream.  I like the former even better, but would limit time in the palace to an hour a day and exiting would drop you back in the mundane world exactly where you entered it from.

Why visit there?  It's the dungeon of a mind.  You might find there:

• unique spells
• alchemical recipes
• secret treasure locations
• martial arts techniques
• battle plans
• secret trade routes
• faction relationship maps
• blackmail secrets (of others or the palace owner)
• serial killer burial sites
• Western March style maps of a region unexplored
• monster classification schemes, along with the monsters!
• daily routine (for assasinations)

You might use it as a way to set up a classic murder mystery where, in addition to the scene of the crime, investigators have access to the murderer or victim's palace.  Perhaps multiple people knowing the incantation can access and change the contents of a palace from different locations, making it a means of long distance, although cryptic communication.  Perhaps you could perform Mission Impossible style (the original cool version) missions where you acquire the incantation, access the palace of a living person who is still using it,  and change it without them knowing to influence them politically, romantically, financially.

The palaces themselves could be locations the players are familiar with.  Perhaps the palace owner is very familiar with that Snake Cult Temple.  Imagine how freaky it could be for players to revisit a dungeon they had cleared, or a tavern, or keep they are familiar with.

As a treasure item, allow a player to create their own palace, and only thus become an alchemist.  Or maybe require one for the vast amount of data needed to research a spell.