Welcome

Welcome is not how those who are left on Sharitarn by the Vortex usually feel precisely. There is exceptions, especially during the relative calm periods of activity of the phenomenon, but for most people first step is hard.

Desoriented would be a more likely description. Scarred also fits reality in most cases.

You are now calling those people cowards, but consider things from their perspective for a moment. You see a swirl opening in the air close to you, a few meters above you if you follow metrical system. Before you can fell curious about it pull you and what is close to you, people, animals or objects, and next thing you notice is the ground moving fast in your direction. Granted, is a soft floor probably, a lovely carpet of living grass... but being soft does not make this grass comforting enough for make the entire experience feel 100% like a welcome.

Now you are on this lovely carpet of grass, perfect like a painting, and it goes as far as you can see in both directions. Only in both directions, because it is a corridor of a few dozen meters. In both sides it ends in a perfect border, and beyond this what you see is an wild landscape, on the other side there is the same thing but the land is far different. If you are brave and curious by this time you already made the first attempt of walk beyond the grass into the wild, and already noticed the invisible wall that makes impossible to do so.

Before you reach that wall however your cellphone exploded in green flames, every piece of modern technology abandoned you by the same door it used. So, if you had a pacemaker your problems are all in the past, but otherwise you probably have a ugly painful burns somewhere in your body.

GREEN LINES

A SOFT BEGINNING

Now you decided which identical direction you like better and walked until the end of this Green Line. Smart and brave you realized fast that stay sitting on the empty spot where you fell does not provide you with the best chance of survival you can have. So you pick one landscape to be by your left side, let the other stay at your right, and make space between landing spot and you.

Chances are that by this point the only two things hard to explain in your experience will be the Vortex itself and the invisible walls. And if you have the habit of drink too much or happened to be sleeping maybe you lost the Vortex, then would be only the invisible walls. What you see in the territory is likely to be ordinary enough to you, plants may look odd, animals more so if you happen to see any, but unless you are a Biologist or have survival training by some reason all you have are mountains, deserts, ravines, lakes, or something of that sort. Floating mountains and rivers are rare in this Age, so chances are that none of such things will be visible from your Green Line.

You don't know it yet, but what you have around you is a planet you could never have heard about or imagined. In a Universe where magic is a main force that decides wars and brings the dead back to life.

Where slavery is legal and not only in some places but in every human settlement. Where most nomadic tribes, considered barbaric by civilized people, do eat human flesh. Few civilized populations follow the practice but they have no problem of accept the existence of cannibals and even make business with them from time to time.

Countless species live in this planet, and many are as intelligent as humans, or more so.

Humanity rules here, but not as a unique body of state. For all you can tell as a common person the humans who impose their will by the power of magical flames could be giant ants with eight brains each, or anything just as alien. What you see are Bronze Age State Cities in constant state of war with their neighbors, Caste System, a few exotic details that don't fit.

If you are women, by the moment you find out half of that you will be a collared and branded slave, probably with years or experience in serve and please the whims of free men. Long before you learn the local language you will have been sold in public auction a dozen times, naked. Raped countless times. Whipped, starved, left to sleep in cages naked or with only a blanket to shield yourself against the cold.

If you are a man, and you are not dead yet, that is because the locals found use to you. They seldom slave men, but seldom is not never. As a slave you are likely to be given the low tasks considered to heavy for female slaves.

If you are still a free men, that means who ever found you decided that you may be a acceptable member of his community one day. At any instant that opinion may change, and you being alive will be a mistake easy to fix. You have no rights until you earn your place as an adult member of your adoptive nation.

A long walk has to be made before you earn the status of citizen, and the rights that come with it. This path looks you in the eyes, smiling with mean eyes and sharp fangs.

Now tell me, brave fellow, that those involuntary immigrants who feel fear when they see Sharitarn for the first time are pitiful cowards.

Manifestation

The Vortex: manifests as a gentle drain that kindly attracts people and everything else not nailed down with very strong nails to itself. Accepting everything and everyone as unconditionally as an maelstrom. Its a heart touching image, but unfortunately don't last long enough to be looked at properly by those in its range of influence.                                        As for those who see the phenomenon but are too far to be carried by it, they are left with no memory. All registers of the Vortex disappear with it, from biologic memory and from artificial ones. What is gone is gone, and people often notice the meaningful absences in due time. More often than not they will construct explanations more satisfying than the true, that is a inter-dimensional hungry cyclone which leaves no register of its occurrences.   
   The Vortex Lines (or Green Lines, as the common people call them): manifests as long lines of perfect grass, which look too straight to be natural. Invisible walls isolate it in from the rest of the world in the both sides, protecting those inside from any dangerous climatic event, or predators.            Animals don't enter the line if they can avoid, neither do plants. And things don't accumulate on them because after a couple of hours without moving the ground start absorbing everything. Give a few days, weeks for larger things, and will be no sign left of what came from the Vortex. 
      Usually some local authority take control of each end of any given Vortex Line, and keep it. They are an valuable asset, and also a significant danger. 
       The Vortex is a natural phenomenon, but the Vortex Lines are a arcane creations. One of the major accomplishments of Mage's Brotherhood.  

Type

Natural

To fall on a different Universe with only your clothes (and is some cases not even that) is a common fantasy of many people, I suppose. Not as common as to be naked on the school not remembering why or how, probably, but common enough. You see movies, and books, and a entire gender of computer RPG based on that premisse (the displacement to a different Universe, not the naked stuff). 
        Reality seldom matches imagination. Sky, for instance, is pretty boring here. No three moons of saturated colours, no big planet with rings or binary suns to talk about. 
           You can actually see the stars on Sharitarn, which is a thing no one does on Earth. Since there is no place on Earth where you could stand that isn't surrounded by far too much artificial light all night. Every night. However, any didactical simulation of observational Astronomy would give you the same sky you see on Sharitarn. Well, not really. 
           Is not the same, just identical to every detail. Almost. "Moon" colour here are a bit different. If you pay attention. 
            You are surrounded by information about cultural, legal, Historical, differences. I'm not going to talk about food, clothes, or language either. Castes, Magical Ways, weird religions of locals. Weird religions of other iis like us, but from different Parallel Planets. Centaur's fecal matter. Wild folk cannibalism. All that is fine and well in terms of exotic experiences. 
             Once you digest the major information, all that change in your mind, not at once but bit by bit. The major information is that it is YOUR world now, the only one you will have up to the day you die. Here is real life, where you go to sleep and awake (if you awake at all) to a new day. 
             Desperation is a feeling no Earthling ii is strange to. So allow me to point you the direction of some elements that may help. While I mention one detail or two about the landscape. 
               Compared to other recently arrived iis we are the lucky ones. Because our home planet is the Parallel Planet tuned by the Vortex. What that means is that by far most iis arriving on Sharitarn come from Earth. Has been like that since about 1700. Our year 1700, 'Ey' 1700, Earthling year. Time passes here exactly as fast as it passes home, and that means we have here generations of Earthling iis. 
                 Families from all parts of Earth came to Sharitarn, same way you did. There is no correspondence from the part of Earth you are from and the part of Sharitarn where you arrive, therefore you will find a mixed Earthling culture everywhere you go. When you find Earthling iis up there, I mean. 
                 First Earthlings came two centuries before 1700. In some parts of South Continent you find medieval castles build in European style, with Japanese architecture inside, and the best possible versions of Brazilian regional food being prepared in large pre-colonial kitchens. Is not the same mixture everywhere, and you will not find the exactly "Pos-Unification" cultural flavour anywhere. Still, that isn't an entirely alien reality. 
                  You can easily get yourself clothes that are decent approximations of what you used to wear on Earth, minus the electronics. And would be wise of you to add a sword to the mix. 
                   Glasses are the trickiest, and most expensive, part. Since transparent materials are expensive here. 
                There is no computer games here, on account of the lack of computers, and that's a huge unreplaceable lost for most of us. No amount of real duels to the death, and sex with pleasure slaves, can replace the emotions of play a online game. We have books here, however. That's something!! Every language from our planet is here, on their books. Comic books too! Well, they do not print things on large numbers, so you can imagine how expensive their comic books are, but they do have some. 
                  They have cows, not many and not everywhere, but they do. Pigs too. No chickens, unfortunately, not as far as  I know. I found no half decent whiskey, rum or wine, but there is something in a Feudal Domain three days north from here that tastes a lot like vodka. Bier is hard to find, but that can possibly be because my standards in that area are higher than average. 
                Fact is that locals do not understand our taste for drinks, alcohol is far less relevant for them. They prefer to smoke instead of drink their poisons, mostly. And incline themselves to substances that work like LSD or "magic" mushrooms, instead of alcohol, tobacco or marijuana. 
                 My point is that you do find alcohol, tobacco and marijuana around here. With no legal restrictions to buy and consume our Earthling recreational drugs. More often than not are descendants of Earthling iis the ones making those products in their farms.
                  Then, naturally, you have music. People sing their songs, and pass them from generation to the next.                          You will not live your life locked in a fake Earth, if you are smart. There is no going back to what we lost. Still, some now and them, makes a world of good for an involuntary immigrant to feel a bit of home in this strange Universe.                                             Earthling food, smells. A familiar song played on a guitar that almost could have been on Earth. Remember that, if you will. 
                      Whenever life on Sharitarn start feeling like too much, too heavy weight, look for one of those Peasant Settlements or Feudal Domains where most people are Earthling descendants. Or even for a "Little Earth" gueto inside some big State City. Prices will probably be somewhat higher than what you are used to, since that's all 'exotic' here: do not worry about. Is money well expend.