What is Myriad?
Let's see if we can come up with any ideas of what Myriad is and how it relates to Nemesis.
I'm hoping Myriad might end up being a new exogenous civilization. My theory is that after the anomaly several shards will appear ala the ExoPre that just move about sowing chaos where ever they land and maybe in the form of red portals.
Nemesis are the allies of the Myriad much like the Enlightened are the allies of the shapers and the Resistance are allies of the N'Zeer.