Publisher's Description (from http://www.worldofmunchkin.com/extras/christmascard10/)
Have a Monstrous Christmas!
Our third Munchkin holiday card is all about the monsters! Santa wants to make them easier for you to kill -- or harder for your opponents, whichever you prefer. Just because it's the holidays is no reason to stop being munchkinly!
Munchkin Monstrous Christmas Card Rule
Once per game, if you have a Munchkin Monstrous Christmas Card on the table, you may use it as a +5 or -5 enhancer (adding or subtracting one Treasure, respectively -- minimum 1 Treasure) to any monster pictured on the front (the Gazebo, Gelatinous Octahedron, Net Troll, Plutonium Dragon, or Potted Plant), as a gift from Steve Jackson Games. Limit one Holiday Card per player per game.