Spoilers ahoy!
For those who aren't familiar, Ehlnofey are those spirits who sacrificed themselves to the Mundus to become Earthbones/laws of nature and/or the progenitors of humans and elves. Read these books to learn more: http://www.uesp.net/wiki/Lore:Before_the_Ages_of_Man, http://www.uesp.net/wiki/Lore:The_Annotated_Anuad, http://www.uesp.net/wiki/Lore:The_Monomyth.
They pop up a couple times in ESO, so I thought I'd collect what I've found so far and write it up.
The first thing I ran across was in the Grahtwood: the Bone Orchard, an ancient Bosmeri cemetery purported to bestow Y'ffre's 'final sleep for the lost.' The center of this cemetery is a large hill crowned by a great tree, which is actually the giant skull of a being named 'the Destroyer' by http://www.uesp.net/wiki/Lore:Last_of_the_Old_Bones, but otherwise known as Dringoth. This creature - apparently an animate skeleton - trashed its way across Tamriel until the priests of Y'ffre put it to sleep by planting a seed in its skull under a shrine to Y'ffre. The Bosmer later brought others of Dringoth's bony brethren to rest under the bows of the tree growing through his skull as they feared that they, too, would take to wandering again and wreak havoc on the world. http://imgur.com/a/EkyWQ.
Nothing ever comes out to say exactly what these creatures were, but one of the http://www.uesp.net/wiki/Lore:Bone_Orchard_Research of a Worm Cultist researching the Bone Orchard speculates that they were the Wandering Ehlnofey, and I think it's pretty clear that that was the intention.
The other encounter I had with the Ehlnofey was in Glenumbra, where they were much different. These Ehlnofey were quite different in form, and seemed to be more elemental spirits than anything else. http://imgur.com/a/bRwCJ, and were aligned with the http://www.uesp.net/wiki/Lore:Wyrd_Tree_verse, which seems to share a thematic commonality with the storytelling of Y'ffre.
So we've got two sets of (apparent) Ehlnofey, both of which are associated with a tree. In one case, the Ehlnofey guide, protect, and nurture the tree. In the other, the tree traps them and prevents them from ever truly dying. I guess this could reflect a difference in mindset among the ada who became bound to Mundus - some accepted and welcomed it, and others either regretted their choice or were confused by what was happening and became restless and uneasy.
We also see that they can take several different forms and functions - some became laws of nature, some nature spirits, some giant bone-beasts. I've only gotten through part of Grahtwood in the Dominion and a bit of Glenumbra, so I wouldn't be surprised if there are other tidbits on Ehlnofey still to be discovered in ESO. Screenshot and post them here if you find any!