A meeting of those who share the same basic soul with one another from all over the multiverse. The one that Lady Eiraiha was called to showed her that alternate timelines and dimensions had caused a near infinite number of others to come into existence, such as Emmy and many others besides. To call a soul moot, one has to deliver a binding crystal to all those to be brought to the moot and then tie their souls together through a complicated spell.
The spell brings them to a sort of aetherial dimension while remaining in the same place at the same time. The host can then address all souls so gathered and provide rooms for groups of them to talk in. Though very costly in power, the spell seems to last some 5-6 hours if cast by a (former) Principal Goddess of advanced age.