bullshit...its incorrect grammar it should either be The Great Devourer Has Come or The Great Devourer is Coming
actually, that
is correct grammar. The English language is odd that way. Let me give you another example you may be familiar with.
"The Lord is come." from the classic carol,
Joy to the World.
really the phrase should read (in current English usage) "The Great Devourer is
here."
However, the word
come is substituted here as an "unaccusative intransitive verb." This form of usage was much more prominent in earlier versions of English, dating from the 1650's (perhaps earlier) all the way through the 1700's (with some instances all the way up till the 1900's).
Common "American English" usage would have us believe you are correct and that GW is wrong. However, in this instance, you both are correct. GW used this earlier form of English usage to display the archaic nature of the phrase, also attempting an aire of "fancyness".
In the early 1900's, people started to substituted the word
has for
is in the phrase. And therefore we start seeing a more "past tense" nature in descriptions of real-time events.
your grammar lesson for the day,
CP
EDIT: Here's a bit of reading for you.
http://en.wikipedia.org/wiki/Unaccusative_verb