Its best case scenario is on a card like Apex Devastator, which enters as a 10/10 hydra and triggers four times, once for each of its extra heads
The only two sets to use the mechanic so far are Duskmourn: House of Horror and Duskmourn: House of Horror Commander
For example, if you control Traveling Chocobo ("You may play lands and cast Bird spells from the top of your library.") and Jidoor, Aristocratic Capital is on top of your library, you can play Jidoor, Aristocratic Capital, but you can't cast Overture
Three and four drop Dragons are the bread and butter of this deck, and you dont even care about Chaos Dragon being un-directable you just care that it can deal eight damage with Sylvia
The high power also makes it a natural pair with many cards that care about a creatures power, like Gwenna, Eyes of Gaea and Gimli's Reckless Might