A question that frequently pops up in the comments on the main map from those who haven't read the description (I'll admit that it's long and that I should do something about that) or looked through the rest of the gallery is 'why no Essos?'.
Fear not, Essos does exist in the Midgard Project. I have been working on it for almost three years now (for some reason) and in that time I have discovered just how intertwined the culture and history of Essos and Westeros are. One does not simply cut Essos out. It, along with Sothoryos, Ulthos, and Bethesda's Akavir, reside in planes of Oblivion.
Oblivion is a cosmological concept taken from the Elder Scrolls franchise and here is mixed with the portal mechanics of the Salvation War (excellent read though not for the religious) and quite a bit of originality (oh gods not OC! Anything but that!). This is expanded on in my work The Other Local Neighbourhood.
Essos and co are located in R'hllor's own plane of Oblivion (R'hllor being the only god in ASOIAF that seems to actually exist) with a continent-spanning imperceptible (across the visible light spectrum) portal a few miles off the Westerosi coast. Akavir is a similar situation. Here's why.
Incomplete official maps
The most complete maps of G.R.R.M's world come from the Lands of Ice and Fire, which are an excellent collection of posters that I'd highly recommend. However the map of the 'Known World' is just that, the world as known to Westerosi maesters. While Westeros itself fits nicely into Antarctica/Atmora with its Lands of Always Winter, the other continents don't have nearly as complete maps. We know very little of Essos' far east, Sothoryos, and Ulthos I am hesitant to speculate in detail what they look like beyond the borders of the map. While the same is technically true for Tolkien's Middle-Earth and C.S. Lewis' Narnia, those are both much smaller in scale and fit nicely into Afro-Eurasia. As it is, Middle-Earth was supposed to be analogous to Europe.
What we know of Essos is enormous. At the current scale (which has been revised in the unreleased HD version of the map), it wraps all the way round to Australia and eliminates Aotearoa entirely. The Summer Isles are well south of the equator and would overlap with Valinor. Sothoryos has been hinted to be even larger and Ulthos is just a huge question mark. Basically it's a world unto its own and cannot be accommodated on the globe without removing everything else (except Tamriel maybe). The 70:30 ocean to land ratio is extremely important to the global climate and a world with more land would look very different. This ratio is why Greenland is gone, Harad is significantly smaller than Africa, and Westeros is smaller than South America. I had to fit Tamriel in there somehow so both Essos and Akavir were shipped off-world.
Years of research has (hopefully) left me more knowledgable of geography than most (outside of actual academia), and Essos is weird. The Bone Mountains are longer and wider than any mountain range on Earth and the Great Sand Sea beyond them appears to be a gorge that would give Mars' Valles Marineris a run for their money. What happened to the Valyrian Peninsula is also not possible with our plate tectonics without a global mass extinction. G.R.R.M has stated that you're not supposed to take it at face value, but this makes the farthest east impossible to map accurately.
Here we go onto the species found in Essos, particularly those of the lands beyond Asshai. The problem is ghost grass. Ghost grass is described to be milky white. Plants are green for a reason, and that reason is chlorophyll reflecting green light. This leaves us with a bit of reasoning to explore.
- Ghost grass utilises a different pigment to chlorophyll in photosynthesis - This is unlikely. Evolution runs on an if it ain't broke, don't fix it principle. If the pigment it uses was advantageous, ghost grass would have overrun other ecosystems early on (as per the Dothraki legend). While the grass does readily outcompete other plants in it's native range, it hasn't overrun the continent. However the plant is white, meaning that the leaves reflect all wavelengths of light and thereby prevents photosynthesis from occurring (using visible wavelengths).
- Ghost grass does not photosynthesise - The success of plants is due to photosynthesis and any plant that doesn't would soon find itself outcompeted to extinction by those that do. Therefore ghost grass must photosynthesise but with a non-visible wavelength such as ultraviolet. This means that...
- Something is up with the lighting. Plants and animals utilise the wavelengths of light that the Sun puts out the most. For a plant to get away with not using the relatively abundant red or blue wavelengths (I know green is the most abundant wavelength in visible sunlight but the plant would be red or blue if using that) then the environment must be devoid of those wavelengths and therefore lit by something other than the Sun. This is fundamentally incompatible with our own planet, but perfectly fine inside Oblivion.
Not to mention the 'black jungles' of Ulthos.