Most High Imperials are humans, tought there's a minority of scorpionids and elves. In the religious question, they are followers of the Cult of Sazzar. They have a code of honor similar to the one of the nomads.
Marriage is a formal and spiritual ceremony officiated by the clergy, you can only have one spouse and chastity is expected, but you are permited to have a lover for reproduction if you are part of a mixed couple.
Dawn Kingdom, High Empire, Sazzar Cult