Okay, a bit of a weird question here, but I figure there are lots of people who play D&D, with lots of different backgrounds - so maybe someone knows something about what I'm asking.  Long story short, I've got an idea in my head for a D&D story setting, and part of it hinges on a world (planet) with a radically off-kilter tilt.  Basically a terrestrial world (silica crust, etc.) with an axis of rotation sort of like Uranus.  In my mind the planet is in about the same position relative to the sun as Earth, so the year would have the same duration, etc.

My question is, how would this effect conditions on the surface?  For starters, one of the poles would spend approximately 1/4 of the year facing the sun at all times, while the other is in perpetual shadow, only to have that reversed for a similar amount of time on the other side of the orbit.  At the equator, you'd either live in a months-long twilight (sort of like being in Alaska, say), or would have normal day-night cycles when the year is in what we would consider spring or autumn, and the sun is perpendicular(ish) to the rotation axis.

My thought is that most civilization (such as it is) would cluster around the equator, as it would experience less violent temperature extremes than the poles.  Near the poles, maybe highly-specialized species (flora and fauna) that are adapted to the really hot and bright but then really cold and dark yearly swings.

Just wondering if anyone has any supplemental thoughts, or knows something about how this might effect plate tectonics (lots of volcanos?), or something random.  More bits of detail could help build the setting.

I mean... yeah, it'd be pretty unlivable near the poles, though considering this is a D&D world, it could be that those places are home to certain creatures, such as elementals, which either go into hibernation or return to their home plane during those times. If some magic was solar-based, it would definitely be a great place to gather/harness magical energies during that time. Also, undead like vampires might live in the dark realms for a time, but again the constant shifting makes it tough. A Castlevania-type moving castle situation could be fun, though. Races with darkvision, or even underdark-style races might crop up around the areas that are constantly in darkness, or might surface during the time those areas are in twilight.

I don't really know much about the actual astrogeological stuff, but in terms of fantasy stuff you could definitely play around with themes of light/dark, hot/cold, and having to endure harsh/dangerous conditions for a long time, sort of Game of Thrones-style.

Aarackocra nomads. That's what I get. The most highly succesful race on the planet is birdmen, who have learned to move with the light, on a perpetual journey around the world, staying just where they like it, when the dormant prey wakes from it's icy slumber, the aarackocra swoop in to hunt, filling they sky-satchels, and moving on the the next Eyrie. The Huntsmen of the Dawn. 

Each Eyrie is itself a bastion of civilisation. Unassailable unless one can fly, nevertheless the base of each holds a village of other, more desperate races and people, who cannot soar along with the sunlight, and have less idle time on their hands to craft the various amenities and luxuries the aarackocra can. And so everyone flocks here to trade or beg, and the birdmen ... could be either benign or malicious bastards. They'd be in an enviable position to rule everyone, and no one would really be in any position to oppose them. Storm an Eyrie? It stops being an Eyrie as the aarackocra just change their route, and now all you have is a tall rock.

Also, it seems ... huge masses of snow would accrete in winter, and melt in summer. It would be a world of ice and water, with basically everything flooded in summer. Well, potentially. I wonder if more water would be caught in the polar icecaps? Making oceans smaller? Dunno. 

Make it a world bigger than Earth and tidally locked to it's sun, and you can have a perpetual dark side, a perpetual light side, and a habitable band at the equator. Might be easier on GM and players alike to have some stability...

My first thought is that sounds incredibly cool. My second thought is that the huge swings in polar temperature would make building permanent structures extremely difficult. The freezing/flooding cycle Acromos describes would be devastating to architecture as we know it; water damage is already the leading cause of structural failure in temperate zones of our world, and the seasons in this one would be so much more extreme that I think stone and concrete buildings probably just wouldn't exist. Elevated wood structures with good drainage would fare better, but they'd still need constant maintenance. Some type of strong weatherproofing (maybe an animal material, possibly magical) could help with that. Earthworks might also be good, but that's getting outside my area of expertise.

I think a cool idea might be a culture of ship-based seasonal nomads who spend the warm periods travelling and collecting resources, then dry dock in the winter to swap goods and repair their boats. Because it would be so difficult to build and maintain permanent dwellings, these people could either group together in a small number of megastructures (splitting the labor amongst a larger group), or divide into numerous tiny outposts.

I'm not a meteorologist, but bear in mind that while the equator of this planet would have less severe temperature swings, seasonal air currents would likely not be kind to people living there. You're essentially imagining a world with one hot side and one cold side that swap periodically. I have to think those swaps would create some absolutely wicked storms for the people in the middle.

Cool concept. (In addition to the plausible universal darwinism thesis) because fantasy worlds are magical, there’s nothing about light/darkness, temperature/climate, etc. that would prevent species from living anywhere on the your planet.