“ A party of adventurers walk along late on an open plain, on a moonless night. Abruptly, War screams, the clanging of metal and death-cries are heard. It is an open plain, and nothing is seen, but the sound of a huge battle is all about them. The sounds continue for a half hour before stopping as suddenly as they started. What was it? Perhaps the ghouls of a long-gone battle, reliving their unfortunate last memories...”
“ (Apologies to GRRM and HBO)
A group of northerners want to bring the Old Gods back to the south. They grow cuttings from the white trees seeking the blessings of the Old Gods on the project, and when the saplings are big enough, they carve faces in them and secretly plant them in forests all over the south, to extend the 'reach' of the Old Gods.
The plan works of course, but the trees are *baby gods*, and behave as such when invoked.”