Thread: Who were they?
For at Erech there stands yet a black stone that was brought, it was said, from Numenor by Isildur; and it was set upon a hill, and upon it the King of the Mountains swore allegiance to him in the beginning of the realm of Gondor. But when Sauron returned and grew in might again, Isildur summoned the Men of the Mountains to fulfill their oath, and they would not: for they had worshipped Sauron in the Dark Years.
'Then Isuldur said to their king, "Thou shalt be the last king. And if the West prove mightier than thy Black Master, this curse I lay upon thee and thy folk: to rest never ubtil your oath is fulfilled. For this war will last through years uncounted, and you shall be summoned once again ere the end." ' -from 'The Passing of the Grey People' from RotK.
It was a nobrainer for them and no 'skin off their nose' if you know what I mean hahaha.
They had spent 3000 years in their state of undead and wished it to be over. They knew their original denial had been wrong, and repenting instead of killing Aragorn and his followers in retaliation for that damnation, jumped at Aragorn's offer. I felt sorry for them and happy their spirits could be laid to rest.
PJ, by using only three, made it a lot scarier. And three better fit the scale of the screen, than would the hoard of the thirty-four actually in Aragorn's party. (Halbarad told Aragorn he had brought thirty of the Rangers of the North with him in 'The Passing of the Grey Company' of RotK.)