Elidibus clearly has plans for the Triad and I have a feeling Thordan's little rebellion was actually one of Elidibus' machinations to awaken the sleeping gods. We all know they're breaking free but I have to agree the way they're changing is odd; they're not just sprouting plants either, their surface is turning to bark from the looks of it. We still don't know what the Triad actually were before they were turned into statues though so it's possible they're reverting to their true forms in some sense.