Duke/Duchess

This is the rank given to monarchs inside an empire. They will generally govern vast expanses of land with a large city as their personal capital while various vassal counts rule other parts of their territory.
Most dukes can afford at least one division and will likely maintain a few regiments as well.

Qualifications

The Monarch realm.

Appointment

Oath of Loyalty to Liege Lord

Type

Nobility, Hereditary

Form of Address

Your Grace

Alternative Naming

Grand Duke, Archduke

Equates to

Independent monarchs are addressed as queens or kings.

Source of Authority

Liege Lord/Personal Power