and here I am.
Though very busy in RL and for threshold, I can give a reaction on this.
I created my map baased primarily on the canon map of Ylaruam, perfectly redrawn by Thorfinn Tait. Then I imposed James Mishler's map over this one, taking into account hex shifting (I remember I;ve chosen to keep the 24 miles hexes into seven 8 mile hexes where the central hex is the hex bearing the non natural information (like cities, and using the dominant number of hexes as the natural information (trees, grass, hills, etc.
Then I used the natural geological movements of the river calculating backwards from 1000AC, keeping the current existing hills into account, and adding erosion, and depositing. This way I got a very slithering river. If I have had access to the Mogreth Map of John those days, I would makes some, but not great changes. overall the same would be applied.
I also used the information from the AD&D2 PC game Stone Prophet within the map, to fill in the blank areas.
As to the location of Nithus (and not Nithius), I indeed would come to the same location aswhat Sturm said;
If you look at the single hill outcropping in the Ylaruam map you can draw a strait line of ten 8 mile hexes southwest from the hex south of this outcropping, to reach Abbashan.
if you would do the same on my Nithian map, you would reach on the Nithian map the grassy location Northeast of the Obelisk north of Nithus.
calculating this back on the Ylaruam map, (And yess...I would placed a whole ruined city their underground burried by blown sand, erosion and magic causing locations to sink) the Obelisk could be found southwest of Abbashan (possibly broken and toppled, but with its secret chambers as per PC game Stone Prophet still underneath) and then Nithus would be south of that...just outside the oasis of abbashan.
as to the sunken ruins of Mogreth I would continue this outcropping as a handy reference. (on the mogreth map this is where the trail becomes a road west of Isshum). There will be ruins of a tower 6 hexes southwest of this outcropping, thus 4 hexes northeast of Abbashan. The ruins of Nithian Rahak would be 2 hexes west with another Obelisk NW of that. Isshum of Mogreth era would be found on the same horizontal line as Rahak, and the top of these line of hexes would go just underneath the outcropping, ...counting the exes underneath this line going east, Isshum would be (4 hexes under the line) east, revealing hidden, sunken ruins must exist in Nithian era in the last swamp hex of the line east of Rahak.
In ylaruam this would indeed be underwater...(2 hexes south of surra-man-raa and then 3 southeast)...i would imaging some lizard like Kna still live in the ruins...where else would they get their magical items...
Oh yes...the statue NE of the outcropping in the nithian map can still be found in the middle of the town Surra-man-raa
I might do a 1 mile Hex map of Ylaruam in the future..it was already on my planing list, but i first have to finish other works...I can't keep creating andf not finishing.
Hope this is info enough..if not...just ask or PM.
Have fun...I now go to bed,..seeyall later