...do not calle up That which you cannot put downe; either from dead saltes or out of ye Spheres beyond.
Wicked Lich of the West
From the top of page 5 of the VV2 Rulebook:
Each Location card is part of a Region. The upper left corner
of the map shows how many Location cards there are in each
Region. To move to a Location, simply place your Longship
standee in the corresponding circle on the map.
If Bjorn has one or more face up Location cards from the Region he is in, then for the purpose of his ability, the Region is explored.
Of note: Location cards sacrificed on previous turns are no longer counted toward explored Regions.