Storyline, so far:

Name of character #1: ? -> Warrior that has learned everything from his father
#2: ? -> His father always told him, as a tail, that his grand-father was part of a secret revolutionary group as an archer, which had pushed him to try as hard as he could to become a great archer
NPC: ? -> Simply a young man with a lot of courage

A messenger of the King (name = ?) comes to query each player at their living place saying the king is convoking all his fellows for an important speech.
Once arrived at the castle (separately: they don't know each other yet), the King's has already started to speak: the sages are predicting an obscure reign of terror all around the world because the Tree of Genesis is actually unhealthy and its getting worst and worst!
The king's asking for some brave guys to begin an epic adventure to discover how to heal the ''ToG''.
Each player will designate themselves and an other guy - NPC - will also be part of the trip (names = ?). NPC will act on its own, but a bit like the dog in So It Begins.
Once this little group is formed, the village returns to their normal activities and offer some ''gifts'' to the adventurers (randomly given!) to help them in their quest.
After, the King invite them to come talk to the sages in person. They enter in a cave (use LoH's office terrain?). The sages come out to be statues (temple statues doodads). They start off with a little introduction about the world's genesis (which is related to the ToG) - that will elaborate a bit on the storyline - and then, they'll talk about some kind of crystal (name = ?) that could - possibly - help the ToG. They indicate to the group that they must pass by an underground passage which has recently been infested by some kind of unknown living species - which aren't known as offencive yet - because the unhealthy of the ToG is affecting the purification of the souls of this world. They also notice the fact that there will be three doors and that's it's important that they enter only the one which seems to be clear of any darkness. The two others contains some epic monsters which got captured by some past warriors (they'll comes out to act as protectors of important ingredients for healthiness of the ToG). Knowing which door to pick could be related to a little riddle (riddle = ?).
Once having entered the right door, they remark some kind of weird atmosphere: the air actually seems to be very unhealthy (use Pylon sprites!). In fact, it'll reduce the players' stamina.
Through all the passage, they'll meet weird creatures which seems inoffensive (critters?). When they'll come back later, the air will have corrupted them.
The underground passage leads to some kind of hill (see Hermit's house blend in Falk's terrain compilation). The old man staying is an old member of the Sun Warriors, a powerful revolutionary group which had the support from the God of the Light (name = ?). Discussing with him will lead to some revelations about this story and a bit of mystification on the sage's alliance and the King's mental healthiness.
Still, they must continue on their trip for the crystal because, in fact, the sages and the King are like this because of the ToG's degradation.
The old man will leave them at the entry of a forest leading to his village: he had once left it because of a problem with the chief but the forest was so dangerous that returning back through it was out of the question. He leaves them an artifact of his revolutionary nation: the (insert God's name)'s lantern. The players can light it up at any time, it only takes a bit of concentration (which means it takes time to light it up). This lantern can overcome any darkness.
At the forest's entry, a little cut scene will be needed so the players can be blinded without seeing it.
In the forest, there is no path, the players will have to explore (re-use the concept of Forest Maze). Before getting out of it, the players will have to find a good spot to sleep: a place with less dense forest and some water near it. Not lighting up the light for the night won't prevent them from being attacked by the monsters so during the night they'll get a little assault.
Once the morning came, they'll continue their trip which will lead the players to a forest which seems much less dense (use Webs of Fire's template?).
There are less monsters in there. Still, they'll find a little group of people which seems to run away from the way they were leading to: they learn that the village is under attack by a religious nation (name = ?) which is claiming that it's all this city's fault and that they must eradicate them to gain back Peace.
The players will have to rush their way to this city and help them defend themselves. This is the first big war. It happens in a huge plain. The other nation have spell-casters (mini-bosses).
If they fail, what happens, I don't know yet
Anyways, if they succeed, they'll get to meet the chief and they will receive some gold and items. A prayer will give them spells (randomly selected!). The players will get more informations about the position of that famous crystal they need to get: they'll need to use a boat to reach that place. Volunteers from the village will command it. During the trip, the players will have to fight against different monsters, mostly air units (which implies that the warrior player will not be useful in the battles most of the time. While the others will fight, he'll have to heal the volunteers to make sure their ship don't crash. If he fails, he'll have to lead the ship to the right destination by itself before they run out of food).
Once arrived, they'll find out a devastated wild tribe which will believe they are the responsible of the assault of souls that happened the last night. The shaman, believing they are some sort of wild animals that morphed into humans will cast a malediction on them, dispensing them from speaking the human language and forcing them to talk only in "their" real language.
This new "ability" will makes it harder for players to communicate with the villages, though, they'll be able to interact with some wild animals (these animals are anywhere in the nature. They only attack for their survive).
To gain back their ability of communicating with the human race, they'll have to accomplish a quest for a forgotten god: they'll need to capture an animal alive and bring it to an altar to sacrifice it so that the God regain his power which is directly related to faith. Of course, that animal will be very hard to capture and knocking him out will be hard. He'll appear as a boss.
Once this done, they'll be able to enter the last town of the map, which will lead them to some canyons. At the end of the path, they'll find that famous crystal, protected by a cannibal tribe.
Once being done with this tribe ( ), they'll bring back the crystal to their village: the King's dead, a fog is partially covering the village and some of the villagers are exploding (lol?) and creatures comes out of them. In resume, the situation is critical.
The players will rush to the sage. Arrived there, a cut-scene starts: the NPC gets attracted by one of the statues and he wonders what's happening. As soon as it touches the statue, huge special effects starts and the NPC becomes an enemy. He starts to talk, saying that when the world started, volunteers decided to "sacrifice" their physical being and get their soul somewhat stuck in a pure element to ensure that their mind is free of any subjectivity. Why doing such a thing? At the very start, he was doing it for his nation, but as the famous day was arriving, he also remarked that he would receive incredible gifts/powers from the Gods for his services, including a form of Immortality since his soul would not leave his new physical being (the crystal) for the Heaven/Hell. Once the ToG got corrupted, each sage somehow gained a bit of objectivity, but they were all strong enough to resist to the temptation of being free of moving again in this world while keeping all their powers, all except him. Therefore, he convinced the other sages that he had found a way of healing the Tree of Genesis: they had to make the volunteers leave for a far land containing that famous crystal, the others not knowing the fact that it contained his soul since the ceremony of soul-transfer had to all be done at the same time, at the different places. When the adventurers would have brought back the crystal, an automatic attraction would occur until the crystal reaches the very first owner of the soul (this attraction is natural), but as soon as it would touch both the statue and an other physical being, it would act as a catalyst of soul-transfer so that the sage (previously known as name = ?) can possess the adventurer's body. The only problem was the fact that if the ToG was uncorrupted, it would automatically recall all the sages' souls so that they can keep doing their job, thus forcing him to leave his new body, which is why he must now kill the players, the only volunteers for this epic quest.
A huge boss fight happens in the sages' room and the players will have to figure out that the only way of killing this boss is actually to sap some of his energy so he stops holding the doors shut: he is actually too strong to be fought. Once the doors are unlocked, the players will have to run away, leaving him in this room which he can't leave as long as the other sages are unifying their forces to keep this traitor in there: the players have to make in sort that the ToG is healed before their enemy has killed all the statues (a timer countdown is activated). They'll have to figure out by themselves that they must enter the two doors they were told to not enter to reach boss that will provide the right ingredients to heal the ToG.
The first door leads to some unexplored earth depths and the other one, to some water world which demons and their minions have established, out of reach of the ToG's power.

(Sorry about grid but your not missing much)