Known facts:

The carving blocks something of yours from passing, even when you have removed everything other than the Chaos Grape.
Foo can not pass either.
Foo also has a Chaos Grape.
Chaos Oil can not touch the carving.
The term "Chaos Ward" directly relates to the carving.


Question:

If the carving is indeed a Chaos Ward, why does the prefix not cause it do the the opposite of warding?