Post Apocalyse Blackmoor

Following up on my last post regarding mapping Blackmoor on Greyhawk, let's go in for a closer look at what that could be like.  I'll start with a new map, building on the earlier post and adding better detail. (Edit August 2020; roads added and some other cleanup)

This map is quite accurate in the placement of locations.  It follows the placement of towns exactly as in Arneson's original pre-CHAINMAIL map of 1971, with detail added from his hand-drawn FFC sketch and the maps from the DA and D20 series as needed.  That's why the coastline has a bit more detail.

Here is what I imagined happened, based upon my reading of Greyhawk lore using Greyhawk dates:

540 CY:  The Egg of Coot unleashes a massively overpowered Move Terrain spell on the Crystal Peaks. The entire mountain range is broken up and moved under the seabed around Blackmoor Bay.  The resulting seismic upheaval causes  the land to shift and rise, dries  up seas, rivers and lakes and drastically changes the geography of Blackmoor.  The void where the Crystal Peaks had been instantly floods with sea water.  As the resulting tsunami resides, a new bay is formed between the Black Hills and the Stormkiller Mountains.   

541 CY: Fifth Coot invasion - following on the devastation caused by the seismic upheaval, Coots armies easily sweep across the land.  Blackmoor castle holds out the longest, but falls within a week.  Surviving dignitaries and heroes retreat to the Comeback Inn. The Egg is unable to breech the Inn, but neither could anyone inside escape. It is possible that they still wait for rescue from without. 

542 CY: The archbaron's wife escaps to Dantredun, where she gives birth to the archbaron's son, Bestmo. 

What can we say about this world?  I imagine a place of ruin and desolation, where once prosperous towns are mere ruined piles or half flooded husks where a few poor fishermen eek out a living in the shadow of the ominous Coot.

The elves and dwarves have fled (or have they?), but the great elven forest remains, and has spread eastward, engulfing the abandoned ruins of Jackport.

The Dwarves of the Crystal Peaks are presumed dead, or are they trapped far underground?

Blackmoor Castle is a nightmare ruled by the centuries old vampire Sir Fang (Baron Fant) surrounded by the slaves of Coot, Red Coven Sorceresses, Id cultist and twisted monsters.

The wealth of old Blackmoor lies hidden in moldering crypts, buried dungeons and broken cities.

To the West, the last Noble heirs to Blackmoor have built up the oasis of Dantredun into a small but stable walled town, more of a keep with a small village attached, while still others live a trapped existence in the ComeBack Inn.

The Temple of Id is rebuilt and flourishing.

The Firefrost channel (a river coming down from the Black Ice) is now cut off from the sea, leaving the Western Skandaharians landlocked and warring among themselves.

A great dry plain exists around Blackmoor where once there were lakes and rives - the waters have shifted south and west, but the Root river remains much as it was.

A great swath of the plains to the south and southwest of Blackmoor are now a flooded swamp "the Cold Marsh" which has even turned the dry Valley of the Ancients into a near impassable marsh.  Creatures from the swamps of old Blackmoor have spread and flourished in this expanded habitat.

In short, Blackmoor in the World of Greyhawk is a land of much opportunity for adventure!