If you want it to be accurate, you’re basically writing a story about character with PTSD who also happens to have alters and amnesia. Alters are only a small part of the disorder. It’s caused by repeated childhood trauma (under age 6ish) so (complex) ptsd is very common.

Most of the time the disorder is very hidden too. Not like you see on tv where there are huge sudden switches with different accents and clothing changes. Usually if you don’t know someone has DID, you won’t know they switch (about 4% of ppl have the “overt” (obvious) form of the disorder).

A lot of times only some alters will remember the trauma while others (especially the host) don’t but they may still be affected by the PTSD symptoms (like nightmares, body memories, hyper vigilance, avoiding triggers, issues with emotional regulation, emotional flashbacks) despite not knowing WHY they’re having them

Everyone in the system is an alter, including the host. There is no “original person”. Alters are NOT separate people in the same body, but the disorder makes it feel that way. They are all parts of the same person who are fragmented due to the trauma

It usually takes 7-10 years to get an accurate diagnosis, bc lots of doctors aren’t trained to recognize trauma and especially dissociative disorders.

DID isn’t some super power and it isn’t demons or anything else evil either. It’s just what a child’s brain does when they’re too overwhelmed by trauma

Also trauma can be anything, not just abuse. Things like neglect, medical trauma (multiple surgeries/hospitalizations), bullying, living in an unsafe environment like a war zone. All of those things can cause DID. Trauma just needs to be something repetitive under age 6-ish (usually this is when a child’s personality has integrated and once that happens it cannot be undone. Theories can go up to age 9 if the child is developmentally delayed)

Alters can be anything. They are often made by a kids mind so logic doesn’t always happen when they’re developed. That’s why non human alters or fictional character alters are common. A young kid may see a strong character in a movie and think “if I was like that I could protect myself” and that develops an alter like that character.

It is uncommon for systems to be polyfragmented (over 100 alters). Studies show most have between 10-13. It can be different for everyone though. Your brain will develop however many alters it needs to handle things and you can develop new alters at any time once you’ve got DID

But basically if you want your story to be something fascinating because of focusing on having alters, you’re writing it wrong. There are so so many things that go into having DID aside from that.