The location the Divination leads you to is different each time you zone into Verdant Cascades. The proximity indicator will fill to indicate you are on the right track, initially blue and turns red as you get even closer. Once it fills completely, the Facet of Destruction appears. Exit and re-enter Umbral Grotto until your indicator shows a little blue progress in the bar (see top of map). Then head south-east (see map). On the way you've got to fight several Quetzal mobs.