This is the 12158th most frequent Russian word.
империи
"Empires" (plural form of "империя").
The word 'империи' is used in conjunction with the preposition 'при', denoting the time period of the empire.
При закате империи началась эпоха великих изменений.
At the decline of the empire, the era of great changes began.
Here, 'империи' is used in plural form, describing multiple entities of empires.
Историки изучают судьбу великих империй прошлого.
Historians study the fate of the great empires of the past.
In this sentence, 'империи' is used in the singular possessive form, referring to one's own empire.