While Grand Master of Flowers isnt a particularly powerful or highly played card, nor is it worth much in its regular printing, the exclusivity of the card has certainly made a huge impact on its price
You could easily find yourself in a matchup where its actually good, have it in your opener (and its not a great topdeck), draw three or four extra cards over the course of the game, and eventually lose to The Scarab God
Daleks, Cybermen, Weeping Angels, the Master, and even the Valeyard all put in an appearance here for a deck that cares about making token creatures and a new type of voting, called villainous choices
Its main purpose is as a haste enabling enchantment, but you can sacrifice it later to give a target creature +2/+2
If you do, put that card onto the battlefield and all other cards revealed this way into his or her graveyard
The thing with Mortify is that there are not many quality cards you can play that kill enchantments but also have other useful functionality