The Forest Giants who are they really? Are they of the younger races or are the older?
Perhaps they are as old as the trow. We now they are very secretive and closly connected to the earth. Their comment "the Earth is our faith" could be interpreted as the contstrutcion or maintenance of the Myth world a physical example of our devotion to the Wyrd.
Their beef with the trow is put here:
"When asked of the source of their animosity towards the Trow, all were silent.After a time the eldest among them looked down and seemed to weep, 'It was they who poisoned the soul of iron.'"
Could it be that they lived with out conflict until the trow tainted iron in the Great Orghe Scandal.