The Galactic Empire: An Empire Reborn
Imperial Officers' Manual
Major Revision: 2.0 – 2008.10.31
An adaptation of the pre–Endor document and policies.
RIP 
... Grand Admiral Rank Insignia ...

The rank of Grand Admiral (GA) is a true relic from the Empire's height.

Only thirteen in all known Imperial history: each Grand Admiral was directly appointed by the Emperor, and each directly responsible to him... None of these white–uniformed warlords were confined to any specific territory; their sphere of duty was the Empire as a whole. With identities & assignments absent from nearly all Imperial records, the fleets of the Grand Admirals moved through the galaxy as ghosts in the night, decimating even the most malicious opposition to Emperor Palpatine's New Order.

This rank was granted a thirteenth and final time... Grand Admiral Daemon was the last. After the fall of Grand Admiral Thrawn, GA Daemon led the forces of the Galactic Empire while officially holding this rank. However, following his disappearance, the rank of Grand Admiral was finally officially retired.