Cloister is where the Philosopher sits, better known as Cloister, is a rather old collectible card game, which is famous because no one has ever played it. 

See, to discern the rules of the game, you should gather all cards, but no one knows how many there are. Once in a while someone in the enthusiast's community spreads the news of a new finding, a card tucked away in a dusty box or in a book between two pages glued together, but it is also highly debatable to know for sure if it is genuine or a fraud, so we don't know how many cards has been discovered until now. Some experts affirm that the only authentic cards are haunted. This started the rumor that you have to be a medium to play. Also that the cards come from beyond the Veil.
[You should click on the card or download it to check if you are a medium and detect something... just in case...]

Yes, because also no one knows who invented the game and created the cards.

The name chosen for the game comes from the very first card discovered, the one that started the frenzy about the collection in 1903. It has written on it: "Cloister is where the Philosopher sits. No Eyes to spare, just Windows and Winds and Widows and Wines and Winners. You shan't Win."
All cards are referred to with the first line written on them.

There aren't two cards alike (for now!), but they are quite recognisable.

The cards are cut out from used paper, with misterious pictures assembled together as a collage, reflecting the passion for scrapbooking of early 1900s. The origin of the prints and photographs used for the composition though is uncertain. Their provenience doesn't seem evident. There is a harsh debate among scholars between those who believe all pictures come from the same unknown book and those who believe that they all comes from some sparsely published periodicals, sadly now lost forever.

On all cards there is writings about a Philosopher. Some say that if you read them in the correct order, they'll reveal some great truth. Or they'll just tell a story.
Hypothesis about how to play this game are many, but one of the most accredited is that you should make a combination based on both lenght of words and elements in the pictures. One of the most audacious theory involve building specific achitectures placing the cards vertically in a certain order.
How many can play?
Do you play on your own?
Against who?
Or what?
How do you win?
Are you supposed to win?

Honestly, no one even knows if the game exist at all.

(This is a non-existing philosophical card game created for the "Imaginary card game jam"!  

This was made with Canva using stock images and a picture from a massive late 19th century tome entitled simply "Magic", subtitled "Stage Illusions and Scientific Diversions, including Trick Photography", compiled and edited by Albert A. Hopkins. You can find out more here.)