"The Principle of the Empty Hand"
Virgilio F. De leon Jr.
In the game of Magic: The Gathering , your hand or the number of cards that you have represents your potential power , your ability to cast spells both big and small or to increase your mana base to cast more powerful spells. One of the most crippling tactics in magic is to disrupt your opponents plans by making them discard cards from their hands , faster than they could recover.
Without a hand , a player has no threats to counter or remove your creatures on the battlefield , they have no way to react and they simply will be open for lethal damage in no time. Some of the most classic decks feature this great tactic and standard decks who want to control the opponent always make sure that they have a set or two of cards called discarders. Sometimes a player doesn't even need to remove all of the opponents hand, they just have to remove the "key" cards that they cannot take care of or something that will disrupt their own plans of victory later on.
Planning to go lethal poison damage with your Skithiryx? Then be cautious enough to use a distress to scope out your opponents hand to rid them of any spot removal like Go for the Throat or Vapor Snag . With these out of the way then you can just swing away without any hindrances. Are you playing a deck that cannot handle planeswalkers? Then if you see one the logical choice is to have it discarded where it has no means of harming you.
This ability of spells or creatures to discard cards is also extremely important to predict your opponents next turns.A double edged sword if you will. While choosing what you would want them to discard you could get a full view of whatever it is that your opponents are hiding as well. There are many ways to exploit this knowledge.
A hand full of Lands ensures that they do not have any threatening spells , a hand full of just spells means that your opponent will have to wait for mana and will obviously miss a couple of land drops while you go ahead and develop your own. If a person has too many counters and he can already cast them with his mana base then the obvious ploy is to "bait" the player in using up these said counters , you can summon threats that are easy to cast and won't affect your plans for later , you can reserve your best spells when you really need them. Sometimes the last two cards in a players hands aren't necessarily a pair of counters , sometimes it can just be 2 lands that they are bluffing with. Some people are really with good with bluffing but its nothing a timely Gitaxian probe or Despise cannot reveal.
It is important to know the enemies hand and it is more important to have them have no hand in the late game so that you and your creatures can do the damage to put them out of their miseries. To paraphrase the Romulans of Star Trek. "To be Unknown is to be invincible but with the knowledge that one garners after having so many peeks at a players hand or lack thereof means that victory is only a few card draws away."