When matter and antimatter collide, they explode with nearly 100% efficiency, releasing an amazing amount of energy. Of course, as soon as sufficient amounts of antimatter could be harnessed and contained, it was weaponized. The XXX-XXX War, which ended 400 years ago, saw widespread use of antimatter weapons. The damage was catastrophic. It is estimated that over 800 billion sentients on both sides of the conflict were annihilated. Several hundred planets were left uninhabitable. The armistice agreement that ended the war was followed by a multilateral treaty that forbade the manufacture and use of antimatter for any purpose, a directive most all stellar nations readily abide by to this day, as there are still dozens of graveyard worlds that stand desolate as a reminder of the horrors of antimatter warfare.