The Dark Magicians were a group of summoners who sought to destroy the Council and establish a new order. Led by the prodigy summoner Elheil Lohenheim, they succeeded in their nefarious deeds by summoning the Otherworldly Dragon at the heart of Faimon Volcano.
Trouble began when the spirits began to awaken and attack summoners. It was discovered that the Dark Magicians were behind the awakening of the ruins. Durand, a member of the Council, had been watching them, but discovered their plot too late - with the spirits awakened, the Dark Magicians began their attack on the Council.
The Dark Magicians were unpredictable - their forces were not enough to overthrow the Council. This attack was nothing more than a distraction, and the Dark Magicians were actually after the Relic Storage. Having stolen the Relic Storage, they retreated to the Vrofagus Ruins, where the last relic remained. With all relics in hand, Elheil traveled to Faimon to conduct the summoning ritual to open the Portal to Another World.
Monsters summoned from Another World are too powerful to be controlled by a summoner. Dark Summoner 2 claimed that the summoning was all done in the spirit of adventure, and the risk was a necessary part of progressive magic.
Bad guys do bad things because they're bad. They hate our freedom and cheeseburgers. - Gazroth_Jadinir