Talking about the aftereffects of Aenys first King's Council upon the Reach, is a pointless affair. The king granted more City Charters to the Reach, than any other Grand Duchy, and yet, by the end of his reign, almost all of them were in complete and utter ruin, and almost all his work undone.
Why?
Simply put, the war of the Faith.
As can be expected given the region being the Center for the Faith, and home of the very High Septon Aenys wished to oppose, the resistance against Aenys in the Reach was beyond imagining.
Peasant mobs in the tens of thousands roamed the land, and so, so many of Aenys edicts, and technological reforms, and infrastructure were destroyed by fire, halberd, and looting.
The only 3 cities that avoided being sacked, burned by riots, being put to the siege, or flat out burned, were the 3 cities on the Arbor, who wisely chose to back his King. The four cities of the shield Islands were not oa fortunate.
By the time the whole fiasco was over, the Reach was utterly depopulated, it's economy was in shambles, and 2 of it's most profitable Duchy's were stripped from it, and became part of the Crownlands.
There would be a King's Council that would determine the course of the Reach in the long run, but it was not the first one, and as such, I shall not cover it here.
The only thing that lasted on mainland of the Reach undamaged by the whole catastrophe, is the road network which was planned at the first King's Council, and as such I shall leave a map of it here.
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Extract from "The King's Councils: Aenys the first, Volume 1" by Rohanne Von Tyrosh. Historian serving Maegor the First, the breaker of chains.