Primarily, it may cause you to waste time, or in some cases real money, on cards you have no intention of using
Since theres a heavy sacrifice theme in the deck too, there are plenty of ways to capitalize on them, like Bastion of Remembrance to drain your opponents of life and Pitiless Plunderer to ramp you up in mana
Though its certainly not cheap for a single card, given how unique it is and its lower price compared to other cards on this list, if you want a card that is unique in more ways than one, you could do much worse than this
Three, the change is of a defined duration
What makes a Pokmon card valuable
until the end of this turn, that monster cannot be targetted for an attack nor by card effects