Methinks we have hugely mistaken this matter of Life and Death. Methinks that what they call my shadow here on earth is my true substance. Methinks that in looking at things spiritual, we are too much like oysters observing the sun through the water, and thinking that thick water the thinnest of air. Me thinks my body is but the lees of my better being. In fact take my body who will, take it I say, it is not me.”
(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.