The Great and Gorgeous Mesmer Collective
Some people have pointed out this may be Marjory being sarcastic. The collective is probably not called this, if it even has a name; and she is just poking fun at mesmers.
Given the creativity in the villain team-up names (molten alliance, toxic alliance) I wouldnt be surprised if it was the official name. One can only hop the sarcasm angle is true.