Grand Duke
From AmtWiki
The highest of the standard amtgard Title.
Bestowed for serving multiple terms as Kingdom Monarch. The list of amtgard grand dukes includes many of the legendary names of yore, including Heimdale,Aramithris, Michael Hammer of God, Ivar Nefarious, Rift, etc etc.
A few kingdoms rank Grand Marquis just above Grand Duke, but this is not a standard amtgard title.