After a second thought, I cannot see this as a balanced card.
If it draws from your deck, it is simply broken. It enables constant t3 immorushes; that's how good it is.
If it adds totally random cards then it is fringe unplayable. Due to the totally random cards added, only rainbow decks can benefit from this. But a rainbow deck, exactly because it being rainbow, needs a very well defined set of cards to operate. This card won't help with that. You may get lucky with a few cards, but most of the time you would be better off by playing another copy of *insert any given rainbow card here* in place of the shard.