It is established that a some form of The Deeping of the Steel Realms existed under the Greenthorne long before it was discovered anywhere else. Perhaps it was the start of the Underlands of the Steel Realms. The forest has no known recorded Navel presence of a Numinous Mundi of Helca – perhaps this is why The Deeping manifested under it.
The edges and heavily logged interior of this forest have grown at an accelerated rate in different areas since around CY 8500 – believed to be part of the effects of The Odyssey of Elancil’s Wound. This has resulted in a few new stands of trees, but not much else.