The Advent Group was a combined group formed from Advent Discovery & Salvage Society, the Volunteers of Seiche, The Concrete Town Particulars, and the Organized CommTech Workers of Quire. Formed after negotiations over control of the Stitch linking Gift-3 to Brighton[1], they were one of the major factions in the Mirage.
The Volunteers of Seiche defected from the Advent Group after Echo Reverie convinced their brother, Ballad Reverie, leader of the VOS, to leave Advent. This was a big loss for Advent, and marked the beginning of their downfall.
Grand Magnificent was recruited into Advent after he did a job for them by planting a bomb on The Restitution of All Things. After getting inside, he began to work against them. Eventually, he would have a meeting with Kitcha Kanna and then blow him up, killing him, and leaving the Advent Group without a solid leader. After that, Advent truly began to fall apart, but it wasn't until Even Gardner, after having a fascist-destroying kiss with his boyfriend, Cascabel, took back everything they had stolen and then destroyed The Catapult that the Advent Group would truly be over.