Shouldn't even be writing this plotbunny, but...

Can anyone point me at a Wiki or something that explains how vampires work in the CLAMP-verse? I mean xxxHolic/Tsubasa: Reservoir Chronicles and wherever they sourced their vampires from, like X/1999 or some other CLAMP vampire title.

I know "game" (gah-may) comes into play somehow, but I'm not sure how. Help?