Archduke Ferdinand was an uncroaked warlord for Stanley the Plaid. Along with Ensign Toast he was placed in defense of the Gobwin Knob garrison after the walls were breached, and was destroyed in the ensuing conflict.
As an Archduke, he was almost certainly at least a Noble.
The term "Archduke" implies a sovereign ruler; which Ferdinand obviously wasn't.
The Roman definition is for an important commander with no formal rank (or an alien rank not used by Romans).
Real World References
His name is a reference to Archduke Franz Ferdinand of Austria whose assassination led to the start of World War I. To this he wears a WWI era pickelhaube, and a gun range target.
Sir Leeroy Jenkins
|Chief Warlord of Gobwin Knob||Succeeded by:|