The whole new Rogue deck is focused on buffing Mistwraith, a new card that grows every time you play an Echo card. Spells like Cheap Shot and Pick Pocket can really make it big very fast.
Since Pick Pocket and Blink Fox will give you lots of random cards from other classes, there is a big chance that your Obsidian Shard will cost 0 mana, and you will be able to draw it immediately with the help of Cavern Shinyfinder.
If you suddenly can't find Mistwraith, then you can draw it with the help of Elven Minstrel. Otherwise, just put the good ol' Questing Adventurer on the board and follow the same strategy.