UFO, mutants os indian spirit....
Ok., I was thinking about what could it be, and I concluded that none of the three entities mentioned above could be the "monster".
1° INDIAN SPIRIT:
a spirit doesn't walk like a heavy mammoth (the scene in the shaft).
Also, in the beginning of the movie, we see someone made by flesh taking the camera on the floor.
We see someone (a flesh body) driving the bus (or truck?, I don't remember) when the family try to leave Weaver.
Why would a spirit worship a neutron bomb?
Anyway, I don't think anybody belives that the monsters were spirits...
2°MUTANTS
How could a mutant produce that sandstorm? With their mind?
How could a mutant prevent people from leaving the town?
How could a mutant put that airplane down?
3°ALIENS
If an alien is able to reach our planet, it means that they have a tecnology infinitely superior than ours. They surely knows the neutral bomb and all its propeties.
Why would they worship the bomb, like a primitive people?
Worshipping is also something primitive. I cannot imagine a super advanced population worshipping simple natural phenomenons, like the cavemen and ancient peoples did in the past (worship the thunder, the sun etc.)
Also, do we have any clue about aliens, besides the speech of the druk man?
May be it could be a mutualism the ancient indian spirits do the sandstrom to protect their holy land, and the mutants live there in harmony and in peace with aliens who scaped from area 51.
pelase give your opinion!