It should provide a steady stream of card advantage, and it eats through at least one blank each turn at the cost of 1 life
Second, some amazing sorcery spells were mentioned to keep your hand filled
Shocker, Unshakable is a six cost, 5/5 Legendary Creature that, on entering play, deals two damage to a creature and two damage to that creature's controller, effectively casting Shock twice
So, even though it's not destroying anything, you can actually prevent not only the Ba Sing Se that is already on the battlefield from making any relentless 2/2 attackers, but all future copies of Ba Sing Se
In her desperation to save her unit during the Phyrexian invasion, Felothar called upon these ancestral spirits for protection, enabling her to drive back some of the invaders
Having cards in your hand can easily become a problem, especially later in the game, so any card that allows an easy way to build up your hand is crucial