After doing so, you can look at the opponent's hand, then discard one card you choose
Effects that interact with this zone (and not the Command Zone as well, ala Drannith Magistrate) arent exactly commonplace, though they do exist
There are few effects more potent than simply telling an opponent "no" when they go to cast a game-altering spell
The Eye of Judgment has this built into the core rules
One player has conducted an experiment involving 10,000 trial simulations, posting their findings to Reddit, and found that collecting every card of one to four-diamond rarity would require a player to open, on mean average, 1,536 packs, with a 99 percent probability that the last needed card would be obtained between the 1,437th to 1,640th pack opened
First banned in 2008, Kokusho was then unbanned in 2012 but only in the 99