Slitherine

Am attempting Burgundi (Anyone actually succeed with it?). I sent my mighty force to raid and surprisingly they raided the shaded out area to the north-east instead of any of the known lands to the west and south.

1. I never knew this possible.

2. A turn or two later, part of where I raided is now NOT shaded and seems to be a regionof a new province. Again, never knew this possible.

So can I keep expanding to the north? How do I convert shaded unknown to a potential region? Just by randomly raiding them?

Yeah the edges of the map are full of surprises. I'm not sure what triggers the appearance of new regions, but it does indeed happen!

I like this kind of mini-feature / Easter eggs

Terra Incognita regions can become playable if neighboring regions get some development and with a lucky dice roll. But no, you won't go up to Arkhangelsk here, it is just one region think in width.

This happens a fair bit in the desert to the south of Mauretania. I've seen about 3 regions appear over time.

I expended Eastwards 2 regions deep playing the Gothones (before getting exterminated by loyalty problems, that's how one learns the game). I did naively think that there were fixed dates for those areas openeing to the game. Seems like my actions were indeed actively activating those new frontiers.

I did also notice that the minimap has a special color for those possible areas.