Oxygen isn't a problem if we assume Maraka is still providing photosynthesis on a large scale -- air circulates, much as you can still breathe in the Mojave Desert or Antarctica or even Beijing on a good day. A lot of plants probably WOULD bend towards the light, and that might be worth considering if we were actually providing art direction for the set. Of course, there are some interesting counterpoints: the closer a point to Maraka is to light, the farther it is from water. The world would probably look something like this

~SOLAR END~
>Charred, Mercury-like hellscape, home basically to fire elementals and other infinite-heat-loving things
>Infernal rock badlands, home to super heat tolerant life
>Very Hot Sand Desert, like a permanent Sahara day. So you can live there, but open water can't
>Sea of golden grass, hot prairie like a perpetual Sarenghetti day, not enough water able to survive for LARGE plants. Pretty good for mortals if you don't mind 100 degrees and no shade
(Maraka Begins?)
>Lively hot swamp, where major rivers end in a muddy delta that gets refilled by new water. Insufficent drainage means that the water, warm like bath water, spreads with only ever-shifting burms of solidity. Decent place to live but a bad place to build.
>Twilight Forest, supports large plant life, most normal terrain overall because the light averages out to about the right number of lumens per long time. Starts summery with broad-leafs and fades into fall or winter feeling areas dominated by pines.
>Tundra scrubland, crossed by countless small glacier melt rivers that will meet and become the major rivers of the rest of Maraka. Too dark for trees but has a lot of scrub, lichens, and ground cover. The farther you go away from the sun, the more likely you are to find Permafrost
(Maraka Ends)
> Giant wall of ice. Percipitation earlier is rain, and joins the rivers, but you reach a point where it's mostly snow -- perhaps assisted by pre-existing mountains -- the sunward edge calves off, but as warm, wet air flowing across Maraka is forced up by cold, dry air flowing down from the Night End, it rapidly chills and loses most of its moisture, the solid bits of that accreting into an ice and snow mountain that slides down, avalanching and thawing into the source for a new river when it grows too high.
> High Ice. Elevated enough, it might see the faint hint of a glow on the horizon over Maraka, but the temperature stays below freezing. Rocky areas (mountains largely buried beneath glacier?) are able to be highly civilized only thanks to magic helping their food issues. Not much GROWS here. There might be regions where the ice wall tried to form over water that remain islands/ice cap over the last great liquid sea of the plane. This would be much more livable since the open water would extend into the Marakan twilight band (tundra area)
> Deep Freeze. The only heat is caried on the wind from Maraka, the only life is migratory or has supply lines (good place to put expeditions delving into old snow-buried cities) Little precipitation so it never even pretends to thaw
> Icy Hell. No hint of light, no breath of wind, the deepest dark region is colder than anywhere on earth. It's possible that the edge of the "elementals and special things only" zone is marked where the bone-dry air begins to fall as snow, CO2 percipitating out of the atmosphere to form another mountainous layer of ice. This time, it's dry ice. If you want to do really exotic things with a place flesh and blood can't go, you could even hand wave it being cold enough for there to be "land" of water and dry ice and "water" of liquid nitrogen. Maybe a powerful wizard could visit with protective magic (oxygen wouldn't become liquid until much colder than Nitrogen) but no mortals
~NIGHT END~