The Shards were... Part of a giant gem that all of us hard. The Drabwurld was said to be the origins of all the worlds, you see, and so when a new world was created it was because the gem had been split and parts of it had gone to form new worlds. I'm not sure if it was to hide or because someone wanted it to hide, but... Either way, there were people born into those worlds that had the Shards inside of them and, eventually, they were brought to the Drabwurld to fight for either the Seelie or the Unseelie.

[ Pursing her lips, she crosses her arms. ]

Shards are powerful, incredibly so. You can literally enter someone's mind and manipulate their thoughts and dreams or their memories. I had only managed to learn how to share memories with mine before I was brought here, and even that took so much strength that I couldn't imagine doing anything else.