As previously mentioned, there are multiple locations where there are hard limits of Pokemon packs that customers can get, but the fact that this needed to happen shows that there were plenty of terrible incidents
This effect can be used if it's ever on the field as well, which rarely comes up but is still nice
If not their effect gets countered
Also, when Grimgrin attacks, you get to destroy a Creature the defending player controls, and then put a +1/+1 counter on it
I would recommend just playing her in everything
Gengar has always been a popular Ghost Pokmon from the very first generation of the franchise, so when this mischievous Pokmon finally got a Mega Evolution, it was a huge deal