The expedition is the group that works as the base to enjoy the contents in the Land of Origin.
Any player over level 5 can organize an expedition.

The expedition can be organized when a player over level 5 recruits
4 more players to make a party of 5 and pay 1 gold to an aristocrat NPC
in major cities.

The expedition can own a territory in the Land of Origin, and is
the minimum group that can establish a country.
After establishing a country, you can build a castle and
proclaim a battle with another expedition.