These characters are monarchs of nations which do not have enough of their monarchs represented in Harry Turtledove's works to justify a nation-specific category.

“King Zev was the king of the small kingdom of the Valley, one of the thousand petty kingdoms...

Zev of the Valley

Hirohito, Emperor Showa

Infanta Isabella of Spain

“Mary I of England (1516-1558) was a member of England's royal House of Tudor and ruled as Queen...

Mary I of England

Alexios I Komnenos

Boudicca (Historical Figure)

“These characters held the position of Emperor of Mexico in the Southern Victory series. In OTL...

Emperors of Mexico (Southern Victory)

Agis II of Sparta