It just has to have at least one card in it, and you don't know the contents before opening it
Of course, there are stories of this thing completely changing the game, but in general, there is usually enough enchantment removal floating around that most of the time this will probably do nothing (expect possibly draw out that enchantment removal, but you dont usually want to approach the game like that, especially in multiplayer)
Wild Cantor Wild Cantor and the next card are likely not better than cards I left off, like Ral Zarek, but I wanted to make sure you knew this card existed
There are a ton of good articles out there about this format, and one of them highlights the insane nature that we, as a community, never played this deck into the throngs of Zoroark decks
Lets see what they good God, that is one hell of an attack trigger