I have found THE solution!
You have to change the state of the ghost faction to defeated with a savegame editor!
1) Download github.com/int19h/WarBender/releases/tag/1.0.4
2) Start Warbender and open your current Savegame.
3) On the left site panel go to Factions -> Kingdom of ... (select your ghosting kingdom).
4) On the right panel go to entry "slots" and to entry "21 (faction_state).
5) Change the value to " sfs_defeated ".
6)Save the savegame (overwrite your current or save as a new one.)
7) Start Warband, load the savegame, check if faction is defeated in the faction screen.
If so, wait on the world map for some seconds. ( I just did STRG+SPACE. )
A screen should appear, and the steam achievement pops up.
Check my achievements:
steamcommunity.com/id/kekskiller/stats/MountBlade:Warband
I have unlocked "Golden Throne" TODAY!
Good luck everyone, drink on me!
