The Devout Aelfwar are weakening the Ward in order to draw life energy. The spots where the Ward is weakest are marked with a Life Nexus. By destroying them, we cut off the Aelfwar connection to the Plane of Life in this region.
A Life Nexus is a hub of planar energy that is leaking into our realm. The worshippers of Greenscale use them to power their magic, but now that you've destroyed them, the Aelfwar will be little more than poorly bathed elves.