Erzwungener Additionsfehler is printed in the fantasy Munchkin color scheme, but it can be used with any card game in the Munchkin series.
A rough English translation is:
Forced Addition Error
A just-played monster enhancer (even one that makes the monster weaker) is either +1 or +20 (the player of this card chooses). Does not affect the number of treasures added or subtracted by the monster enhancer.