The Central Plains is a Dominion within the Holy Grand Empire that consists out of four Provinces: the Empty Steppes, Rish-En Tribe, New Ingelheim and the Yak Tribe. As only Dominion within the Empire it is not directly connected with the sea. It's also the only part of the Empire which did not belong to Jingdao or the Apollonian Republic before the Apollonians (Kildari, Aryans,...) were integrated into the Jingdaoese Empire.
With the conquest of the central plains, after numerous wars and a full-scale invasion by the armed forces of Jingdao, the dream of connecting Aryasht and Kildare with each other was fulfilled. It also offered a new home for the hundred thousands of Batavian colonists who were evacuated from their homeland after the collapse of the Kingdom of Batavia.
While formally annexed and the tribes been subdued (the title of Great Khagan being offered to the Heavenly Light) the original inhabitants have barely changed their ways of living: the tribes travel like nomads from region to region and ignore - to the frustration of many Batavian peasants - the borders of the Provinces.
The fights and pillaging that frequently happen - mostly when the Rish-en Tribes and Yak Tribes come into contact with each other in New Ingelheim - during the summer season are already referred to as 'Fire Season', as the victors of those small skirmishes go on raids through the countryside to celebrate their victory.
The Empty Steppes are home to more peaceful tribes, who don't often leave their territory. It's soil is poor and if there is any trade at all, it is trade in Flemish slaves who passed the border in the hope of escaping their homeland.