What Key??????

I have a friend who is in what i guess would be called a death metal band, and i told him i would help him write some stuff since he is kinda new at theory. But i have a song that i am not sure what key it is in, it starts with an add nine barre chord, but because of the tuning i am not sure, the intro goes as follows,
tuned own 1 whole step then drop D<===Thats low
D|-------------------------|
A|-------------------------|
F|-----7-----7-----5-----5-|
C|---3-----3-----1-----1---|
G|-5-----5-----3-----3-----|
C|-------------------------|
Would it be in the Key of F??? Thanks for any help.

from the look of the first chord it looks like the key would be C. Hey... i could be wrong

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And that's the bottomline............

Well, there are a few ways to explain this away. The easiest of which is to say it is not in a single key. The first chord is minor, suggesting a minor key. But aeolian and dorian are the most common minor keys and their respective VII chords are major, and the second chord here is minor.

This gives us a second option. The third minor key, phrygian, has a minor VII chord, and since there are only two chords here each containing the root and the third, we can say that it is in C phrygian. It depends on what the rest of the song is.

Remember that analyzing music isn't always so cut and dry. There are usually a few answers for every situation.

Well...There are some options. One is that it could be in one key, that key is G#/Ab major, in terms of key signature, what sharps and flats are contained in the song. This would mean that the first chord is the 3 chord, with a phrygian tonality, and the second chord is the 2, with a dorian sound. For a death metal song, think of it as a C phrygian song, that would work.
However, since the chords have only roots thirds and octaves, without fifths, it could also be in C#/Db major, with the first chord being the 7th, with a locrian sound, and the second being the 6th, with an Aeolian sound. This seems just as likely to me, if those are the only 2 chords in the song. Solo over it with C locrian or Bb Aeolian and see what you come up with.