I may have shamelessly ripped this from another website whoops
The rules are basically one poster throws a gem into the pile, describing it in some way(what shape it is, what type of gem, color, etc.), and the next person to post has something happen to them, usually a power or something, based on the gem.
Example:
User 1: I throw a glittering blue gemstone into the pile.
User 2: Now you're blue(daba dee daba die, daba dee daba die,). I throw in a pink gem shaped like a hexagon.
User 3: You now have the ability to summon a Mega Sableye! I throw in a yellow triangular gem.
I'll start.
I throw in a shimmering opal.