Byzywork
Very rare1.6%ObjectiveOptionalSingle-player
Have five simultaneous House members as Theme governors (not including you) while not being the Emperor
Needs Roads to Power. Five living House members (not you) holding Theme governorships at once, while you're not the Emperor. The wiki's shortcut: set the "Extra Administrative Realms - Players" game rule to Always, then in 1066 create a custom 50-year-old King of France with five sons and hand each son a Theme governorship via the grant-title flow - near-instant. Organically it also just happens while playing a landed family inside Byzantium, where it stacks with 