Considering that Black Keys are so rare, opening a Black Box only
to find a Griseous Crystal/Pearl (not sure if the latter is in
black boxes but still) is rather disheartening. I suggest make them
exclusive to Gold Boxes only, to give more of an incentive to open
them (Plus they're gold coloured:P) while also making opening Black
Boxes worth their cost. I know that there should be an element of
randomness, but spending 1 million PD to get a key but get a
crystal worth 200k is rather drastic. Furthermore, not everyone can
play Gem Cauldron, due to lag or other reasons.
tl;dr make Giratina Forme Change
Items exclusive to Gold Boxes