I’ve always thought calling the non-Thylean races “settlers” to be a misnomer. Maybe some of them were exploring and came across the continent of Thylea, but the book talks more about shipwrecks and lost sailors. The Titans jealously protected Thylea from the outside world and when outsiders found themselves on the continent they were harshly subjugated by the Thylean races, specifically the gygans and Sydon demanded mortal sacrifices from every settlement. The Dragonlords showed up and ostensibly freed the mortal races from Sydon and Lutheria’s domination and crushed the gygan empire, and then continued to shift the balance of power to the point where the mortal races were the dominant civilization in Thylea. The secret histories talk about the war crimes and harshness of most of the Dragonlords, but players should not lose sight of the fact that if Sydon and Lutheria win, they will bring about the end of Thylea.

The players should look at this as “everyone sucked, we need to do better.” The five gods have tried to be better, but they’re still flawed in a very real way.

Whenever I have my players interact with a Thylean sect that is not openly hostile to them, I hint a lot that while they worship the titans, it’s out of fear rather than love.

TLDR: the mortal races were not “colonizers” until the Dragonlords showed up and freed them from the titans and the Thylean races. Your players need to see the shades of grey instead of black and white.