Since these Bagog-spirits can be lost and a new one gained when a new Queen kills an old Queen who has lost her Bagog-spirit, I see no reason new ones cannot be created. My guess would be that the new Bagog-spirit would actually be the spirit of the former Queen, which makes me think that a Queen could die (and have her spirit become a new Bagog-spirit) while also passing on her old Bagog-spirit to a challenger.
So, that would be my mechanism for new tribe creation. One part gets the old Queen as a Bagog-spirit, the other part gets the old Bagog spirit. We could also note the case of Queen Zagig, who presumably has at least 4 Bagog-spirits. Perhaps this is relatively normal, with multiple Bagog spirits accumulating in individual Queens as the Scorpion Peoples numbers are reduced since the Greater Darkness.
There is also the multiple challenger thing which I don't think is out of the question - perhaps an old Queen, could voluntarily sacrifice herself, as it suggests as a possibility for the shaman status.
Powered by hypermail