"What is a system? What is plurality?"
↳ This website is a good starting point for understanding the basics.
What is an endogenic system?
↳ A plural system not initially formed in response to trauma.
"But that's not possible! DID can only be caused by childhood trauma."
↳ Most endogenic systems do not have DID/OSDD and state this outright.
It is true that DID is primarily defined by multiplicity, but multiplicity is not inherently disordered.
"I still don't believe you."
↳ It's not my job to convince you.
I'm working on compiling more here: https://rentry.co/endogenics (WIP)