[[ keep in mind, everything always has exceptions ]]

rough timeline:
-1100(?) major cataclysm, continental plates shifting, some species went extinct
-1000(?) floods, shrinking of landmasses, some islands sunk, others came up (floods reputedly caused by crying ogre, over a woman who tricked him)
gradually, new beliefs and gods arise
new cities are formed (mostly coastal or island-based)

then the great blazes happened (god of forges screwed up, some molten metal leaked from his forge), making deserts along the contours of the land to where they would rest, giant hunks of solid metal (quickly looted / built around, good resources) which continue to grow slowly (monoliths) and go down deep (where the earth's heat is unbearable).
sieging cities is often about these monoliths
most cities are around one, or on a former mountain or island, and only rumors could tell you why (tactical reasons, artifacts, legacy)

-every 250 years the disaster repeats, but to a lesser magnitude (continents shift, oceans expand).
scientifically sea level stays the same, but to an observer it may look like it's receding or swallowing lands.
all cities have massive fleets, even if moored far away from the sea (sometimes hundreds of years old, some even from the first repeat).

humans survived, by virtue of their skill as sailors

the trees of the world are either enormous and can use salt water, or are small, about a hundred years old most often
the elves mostly live in and around these trees (their main religion is based around the personification of their true tree), and they never have to move because of it. (plenty of humans live among them and vice versa.)

dwarves are masters of submarines and subways, and they move only by choice. their mountainous homes protect them from the sea, both under and above it. high tech is considered like magic, but there are common inventions everywhere - rails, ships, etc.
they also have floating airships ("floating cities" around 4-5 afloat atm), which are very rare and none are new -- all date back to the first and second repeat (supposedly if they needed to make a new one, they could, but they are well maintained and understood). smaller ones are made in large quantities.

technology is slowly shifting to the humans, who are finding common ground from their skill as sailors to airship pilots. they only have the small ones of course. (they also fly for dwarves?) they're unmatched sailors, and have some form of smaller water-based ship-cities (e.g. noah's ark), around which they tend to build their cities once the flood is over.

orcs also survived, and they believe they used to be immortals, cast out of heaven as lesser and disappointing. now they build the great towers of the world, believing that living in the air is their true place. (they dislike dwarven airships - that's too easy!)
they're not savages - some are, but they're a minority (like human tribes irl).

transmutation and repair is the prominent form of magic, but it's not omnipresent (most labor is still done by hand). all the races wield magic, and none are more inclined than others.

elves only live to around 150 (and believe that once they die, they return to the tree to be reborn -- one in every two children remembers a
past life with varying degrees of clarity, but they are still treated as children -- the ones that don't remember are told that they need to be
loved, for their former life must have been one the tree spirit benevolently believed shouldn't be remembered; e.g. very few remember being
soldiers), humans live to around 90, same for orcs (but many get themselves killed earlier, refusing to stop working on towers or fighting
even when they're old, or overworking their forms to be more like gods), dwarves can live to 200 (but most are teachers from 100 onward).

the original mythology (ogre, forge god, etc.) is common among all the races. humans and dwarves don't have patron gods, orcs don't really
count. all races (except perhaps orcs) consider themselves direct descendents of old-race-X, and that their gods thousands of years ago
(or perhaps just before the apocalypse) changed their forms to their image. elves still believe in their main god, since he is ever present,
but humans, dwarves, and most others have mostly forgotten about them, but know this tale.

all races can still breed with each other, and there is no real explanation why it works with orcs too -- perhaps since they really do(n't?)
share angelic blood.

the apocalypses are out of the minds of most people, even though everyone knows about them: "out of my lifetime", "we already have a plan",
"that worked every time", etc.

there are still islands that surface with artifacts of thousands of years ago uncovered from time to time

dwarves occasionally go to war with orcs when their flying cities risk bumping into towers in their path, humans wage war on each other
plenty, but wars usually aren't racially motivated (again, the belief that they were all once the same), and halfbreeds are incredibly common.

psionics get a green light, but won't play a major role in the setting


[[ there are many other races and details, but this seems to be it for now ]]