You'll be able to open them exclusively in Collector Boosters
Even with some recent additions, it mostly dwells in the second and third tiers of the format and has for a long time
It is a truly awesome and terrifying scene that clearly showcases Gyarados' sheer power, making it highly sought after by collectors
With this move I wish Mewtwo's retreat cost wasn't so high because I would get the defending Pokemon asleep as fast as possible then move in a Pokemon like Snorlax who has moves that does more damage if the defending Pokemon is asleep, if somehow I could get retreat costs to be much lower for all Pokemon I would switch back and forth between Mewtwo and another card quite rapidly
Much of Nihiloors power comes from the huge swing in board control you get just by resolving them and triggering their ETB
This version, interestingly, does not make the light blade of the sword yellow, but instead an almost angelic blue which I really like