The use of Hebrew letters to designate earths with a significant parahuman population originated in a presentation by Israeli researcher Abraham Mizrachi to the world security council on the threats posed by alternate universes. Although an inconsequencial numbering convention (chosen as to avoid using the long numeral designation previously used) the use of hebrew letters became a standard.
Earth Aleph was the chosen designation for the main Ravenhold universe, which diverged in 1962 with the arrival of the Aldaars and the subsequent appearance of mutants soon enough other parahumans.
An oddity amongst the known parallel earths, Earth Bet had an almost identical history to earth until 1927 when radio contact was established with the universe’s Venusian population. Unlike many other earths, Earth Bet has enjoyed fairly peaceful 20th & 21st centuries.
About eight million Venusians have emigrated to or have been born on Earth Bet, with a few thousand then moving on to earth Aleph after the two Earths made contact.
Diverging at some unknown point in prehistory – Estimated at roughly twenty million years ago – Earth Gimel is one of the know earths were humans have never appeared, but the only one with another sentient species. Gimelians as they are known on Earth Aleph – Their languages being unpronounceable to human – Are Gorilla-like humanoids with more streamline bodies who stand upright and of comparable intelligence to humans.
One of the least pleasant alternate Earth, Earth Dalet was invaded and conquered by an alien species calling themselves the ‘Hosts’ in 1996 who have set up an occupational government on earth for still unknown purposes. Due to the danger posed by the ‘Hosts’ Earth Dalet had been put under quarantine.
Earth He is a ravaged world which would bear little interest had the presence of parahumans not been confirmed. In the 1970’s Earth He entered a global war which ended nuclear exchange which destroyed the world’s government with what remained crushed by the nuclear winter.
Although the specifics are uncertain the usage of nuclear and chemical weapons have caused mutations to occur, creating twisted aberrations which roam the world. Due to lingering radiation and dangerous mutagens, Earth He is offlimit to anyone but approved survey teams.
Arguably utopia, Earth Vav changed when an alien artifact landed in 1891, bonding the entire world. Although beings on earth Vav have a measure of independence, they are very loyal to the over mind.
Earth Aleph’s contact with Earth Vav have been entirely peaceful, although Earth Vav has been less than forthcoming with explorers, believing Alephi to be too beholden to the ‘old ways’
Diverging in the middle of world war II, Earth Zayin saw the appearance of superpowered soldiers, first by the Axis powers and soon enough from other nations, which caused a prolongation of the conflict, with the aftermath further destabilizing the rest of the world.
As a whole Earth Zayin is less technologically advanced, remaining at earth Aleph 60’s level of technological development, and also more unstable with many countries splitting into small fiefdom ruled by superhumans with a xenophobic bent.
Although a little under eight hundred worlds have been discovered, very few of those worlds are interesting and have been largely left alone. Still certain patterns exists within those worlds.
The current understanding is that all earths diverge from a (still unknown) primary earth, with events happening beyond that divergence point no longer mirroring the primary earth.
Wild worlds are earth where humanity does not exist, some of which have attracted the interest of corporate or governmental authorities as potentially exploitable locales.
A grim spectacle, Dead worlds are worlds where humanity had gone extinct (or have too small a surviving population to matter) after having existed for a significant era. Dead worlds discovered have been destroyed by nuclear warfare, super volcanoes, comets and in one instance a particularly effective pandemic.
The slightly more mundane worlds are extremely similar to Earth Aleph’s pre-divergence point until their own divergence points. Many such worlds have had fairly minor divergences, but others are virtually unrecognizable.