Mine is Northumberland. After you win the independence war, you get the event „the king in the north“, making you a kingdom. Then you have to choose your ruler. You can keep your generated ruler, choose a Percy, a descendant of Ragnar Lodbrok, giving you a restoration of union cb against Norway or choose a Lancaster or York (the opposite of who rules England). The Texts for that are „the Lancasters send their regards“ and „the north remembers house York“.

Edit: Since many of you said Asturias and Bulgaria: I once released Asturias as Byz, not knowing about their ideas. When I annexed them I suddenly got a notification that someone occupied my colonies.

And I once released almost all releasable nations in Eurasia and then started as Bulgaria. After the independence war I switched to Mongolia and continued as it. When I reached the middle east, Bulgaria had killed the Ottomans and conquered Anatolia and Mesopotamia. I almost felt bad for killing it. And since it was one of my first campaigns, I didn’t know about AE. By that point I was fighting a coalition war against all of Eurasia.