Eve is the Queen of the Ancient Robotic Civilization of Nasods, created by humans utilizing the Soul Stone, which was the basic protector of the world, emanating El(The Planet's Lifeforce) towards all, the Soul Stone was protected by the El Maiden, the goddess of the world, and along with her, she chose 6 humans she thought strong and reliable enough to become "Salvatores", Salvatores were protectors and controllers of different elements of the world, to keep them in tact, I'm not gonna name them all, since so far, only Solace (Sun/Light) and Denip(Water) have appeared or been even mentioned in the story.

Salvatore Solace, however, one day, he became greedy for power, and went to get such power from the Soul Stone, the El Maiden tried to stop him, with the help of the Humans, this is known as the "Magic Wars", you guys are gonna learn to hate Solace by the end of the game, I'm serious. Anyway, the El Maiden and the Humans managed to stop Solace, but Humans, as greedy as they are, decided they wanted power from the Soul Stone as well, the result was an unexplained explosion which threw the world off-balance, killing everything in it's range, but the El Maiden, the El Maiden went into hiding after that.

After the Explosion, without the Soul Stone, the El couldn't flow perfectly around the world, Pieces of the stone became what are now known as the "ElStones", they give life and emanate El towards a surrounding area, making it habitable, without El, the area is extremely inhabitable, as it was before the appearance of El.

(Trivia: The only places with confirmed Elstones are Ruben and Hamel, Velder presumely also has one.)

The Nasods, before the war, were being treated as slaves by the Humans, but robots or not, they were still sentient, so they rebelled, starting a war between Humans and Nasods, like LUG said in their little preview, Eve went into hiding before things got out of hand, and only reawakened hundreds of years later, I'm not sure exactly when, but presumely after the Elsword Crew beats the Nasod King.

The Nasods had to live off the El, after the explosion of the Soul Stone, they went all completely into Emergency Shutdown mode, on the present day, someone, or something, I have no idea who/what, reactivated the Nasod King, and along with him, all the Nasods in Altera, thats when they kicked off the Ponggos (Those guys from Altera) from the mines, and started mining as well (Probably for a more physical form of the El.), such Tunnels were the Contaminated Area and the tunnels in 4-3.

Now, what exactly reawakened Eve was what they said, an Elshard entered her chamber, she absorbed it's energy and came back. What they said on the preview however, is partially wrong, Eve's first reason to go with the group was literally stab them in the back, steal their El and remake the Nasods, gathering revenge on humans, but she discarded that idea entirely, because of Elsword, I believe she also discards the idea of remaking the Nasods as well, as Hamel has quite a few Nasods and she doesn't care about beating the living crap out of them.

There are a lot of other tidbits, but that's the major stuff, also, to whom read what I wrote all the way back then, after a lot of talk with a friend, while 3-3 and 3-4 are entirely canon, all the Secret Missions are not, with the exception of Altera Secret, which is a "Maybe, leaning towards no."

Now, this is the cool and understandable part of the story, after you guys reach Hamel, it makes absolutely NO. FREAKING. SENSE.