We always assumed the earthquake that destroyed Agate Mountain and buried Darkstalker also destroyed the Ancient Nightwing Kingdom, making it look as it does in current age maps. But this never made much sense to me.

Absolutely none of Phyrria's coastline has changed at all in 2000 years (including the waterways closest to where Agate Mountain used to be) except for the Nightwing's peninsula? That's a little too convenient.

Re-reading the Moon Rising GN recently, I noticed this comment from Moon that the Nightwings are both in charge of creating the maps of Pyrrhia, and have been hiding any evidence of their kingdom.

My theory is that the Nightwings had been purposely creating hugely inaccurate maps for the last 2000 years.

To prevent other tribes from finding their old kingdom, (or worse- discovering Darkstalker himself) they made their old territory look smaller and less interesting in all its depictions.

In truth, the Nightwing peninsula is nothing like the current map depicts it. It looks identical as it was 2000 years ago in reality, just like the rest of the continent.