Tiffany, it's a complicated sentence, with a long, complicated predicate phrase. The subject is "Language." Everything else in the sentence is the predicate.
I'll break it into smaller sentences to help better understand it:
Language seems skillfully drafted.
Language often seems so skillfully drafted.
Language is drafted so skillfully that one can hardly imagine how it was created.
Language is so skillfully drafted that one can hardly imagine it as anything other than the perfected handiwork of a master craftsman.
The sentence is a quote from Guy Deutscher in the book THE UNFOLDING OF LANGUAGE. The meaning of the sentence is that human language is so elaborate that it is hard to imagine how it could exist unless a master craftsman created it.
I hope this helps!