I see more the battle of Pendraic as a parallel of the
Battle of Adrianople, which precipited the fall the Western Roman Empire.
I'd say Vlandia is rather the Frankish, filling the role of romanized barbarians who build up successor kingdom in the Western Empire (Francia especially). Though yeah, it's more of a 8th-9th century aspect than 5th.
Sturgia is obviously the pre-settling Norman, the whole Viking invasions thing.
Battania would be the Celtic tribes of Albion probably, though they could also be a somewhat out-of-era call to Gauls and the like.
Aserai are the Persians, and the Khuzait are the Huns, both which fall pretty much exactly in the "5-6th century" thing.