"With the Vale now safe from harm, Erutan Revol turns his attention fully toward Channon. The center of trade for this region lies at the city of Ginvil, which was built at the expense of the surrounding land. Erutan Revol cannot abide this, he will liberate it from the humans before moving on to the capital city of Rylos. They shall pay for what they have destroyed!"
"The only thing between you and the Channon capital of Rylos is the heavily fortified city of Ginvil. Not only is it a blight upon the land, the surrounding forest having been torn up to create it, but it's in the way of your final goal. Defeat Ginvil and show these humans the true wrath of nature!"
Erutan Revol begins his assault on the last fortress between him and Rylos. Avoiding the heavily fortified gate, he finds a secret entrance to bypass their defenses and strike at the center of their town.
The town of Ginvil in the center of the map is heavily fortified, and Erutan Revol starts out massively outnumbered, so he should start out by building up his town while exploring the map. In the southwestern corner, there's a Haven town he can capture if he first visits the quest hut east of Ginvil. The town can't build creature dwellings, but will still grant income, and reinforcements of Preserve creatures will arrive in the town every week.
The easiest way of entering Ginvil, is by using the ferry to the east, and slipping through the crack in the wall that will open when the Haven town is captured and the quest hut visited. Note that, even when the garrisons are bypassed, Ginvil will have an impressive army.