A quick-thinking local Brigadeführer made a deal with the mystical SS society of the Ahnenerbe to take possession of the booty (and to keep it all secret from the mainstream Nazi hierarchy); Reich-5 scientists and sorcerers are using occult rituals and horrific medical experiments to slowly spread their Thousand Year Reich to other realities.
A parallel where city-razing Mongol hordes under Genghis Khan destroyed first Beijing and then all the cities of Europe, where now their descendants (in "current year" 2004) rule an entirely nomadic continent.
When Isaac Newton discovered the secret of the philosopher's stone in 1693, he paved the way for an Alchemical Revolution that has left Azoth-7 dominated by the magical might of Britain, Venice, Prussia, and Spain by "current year" 1780. Notable for having space travel - though whatever Polaris and Sirius may be, they are not balls of hydrogen tens or hundreds of light-years away from Earth.
(The Rivers of London series is also based on the premise of a magical Isaac Newton) In Bonaparte-4, Napoleon sacrificed the romance of an Egyptian campaign (which he conducted in 1798 in our timeline) for a stealthy invasion of Ireland, granting him victory over Britain.
Unfortunately a burgeoning global war between the tradition-minded major states (Sofala, Persia, Andalus, the Bulgarian Caliphate and the Ummah) and the technocratic Jamahiriya of the western continents threatens the existence of this advanced society.
While military applications of scientific research advanced rapidly enough, science as an intellectual pursuit became associated exclusively with death, destruction, and catastrophe (especially after World War II ended with the bombardment of Germany with radioactive dust, killing hundreds of thousands of people).
Lacking the positive fruits of scientific inquiry, the world heads (in "current year" 2004) through ecological disaster and failing economies to a nigh-inevitable showdown between its capitalist and communist societies.
William's survival precluded The Anarchy and the Hundred Years War, and ultimately the "Anglo-French Empire" became a world-spanning power, with technological progress centuries beyond that of Homeline.
They believe other worlds should be aiming to follow their example and have a dedicated program of supporting political and economic groups that reflect their own values—stability, meritocracy and an unconscious prejudice against non-English speakers.
In this world, William Walker succeeded in conquering Nicaragua in 1856; during the American Civil War this provided a way around the Union blockade for the Confederacy that ultimately ensured their victory.
In revenge for British support of the rebels, the United States invaded and annexed most of Canada; meanwhile the Southrons reintroduced their "peculiar institution" into Central America and the Caribbean at gunpoint.
watch each other warily across an armed border that stretches to the Pacific, while India, the Chinese republics and their neighbors expand their economies at the expense of the moribund European monarchies that never fell after 1918.
This premature contact gave the Native American civilizations time to recover from the shock of new diseases and adopt the newcomers' technology; in addition, the early introduction of maize and the potato to the Old World eventually reduced Rome's ability to control its subjects through Egyptian grain.
This parallel world is named for the Holy Roman Emperor Friedrich I Barbarossa, who in this timeline managed to be the great imperial unifier and conqueror that the vagaries of fortune prevented him from being in our history.
Without Hamilton to defend and explain the United States Constitution in the Federalist Papers, it was never ratified and the independent colonies balkanized into nine separate republics across the continent by 1860.
In "current year" 1965, the World Science Council and the League of Nations are putting down all threats to the techno-utopia that has resulted from the inventions derived from Tesla's work.
Examples include Ariane (where the Spanish flu killed 99.9% of the population), Lenin-2 (where nuclear war and unconstrained industry have combined to crash the biosphere) and the worrisome Gotha parallels (where a prion-based disease has turned almost all humans into bloodthirsty cannibals on 19 otherwise dissimilar worlds).
In the "current year" of 1678, various empires based on slavery and human sacrifice cover the globe (except for an Infinity Patrol-supported haven in southern Africa) while an anomalous ice age threatens to wipe out those unfortunate to live in a world where monotheism, democracy and the Greek and Latin alphabets were destroyed almost before they could begin.
Widely regarded as one of the most disturbing and potentially dangerous worlds so far discovered, in this parallel Giuseppe Zangara succeeded in assassinating Franklin Delano Roosevelt in 1933.
His successors Garner, Lindbergh and Wallace proved unable to handle the Great Depression, and America stood by while Hitler conquered Europe and Japan took over most of Asia.
The resulting changes in history spread all the way to Japan, where an increased Jesuit presence prolonged the life of Oda Nobunaga and prevented the closing of the country by the Tokugawa shogunate.
The similarities exist down to cultural and political divisions (resulting in this world's colloquial name) and are assumed by Homeline scientists to be evidence of a "law of temporal inertia" (or "gods with a strange sense of humour").
There are some other ideas provided to make things either easier or more difficult for your intrepid travelers such as Linearity Principle, Oscillating Time, Recency Effect, and Temporal Exclusion as well how communication works.