Looking for some advice on how to handle a specific character I'm working up:

Character is a Changeling Assassin Rogue and I am tossing around a few different methods of how to handle the personality, or should I say personalities, of this character.

I want this character to have multiple different personalities but keep the character completely within the rules of the game.  I've seen a few people while trying to fine tune this idea who dabble with different classes for each personality but obviously that ventures into the world of homebrew and DM approval.  What I'm looking for is purely personality based and for the dynamic of switching up attitudes throughout the campaign day by day.

I'm thinking the character has somewhere between 6-10 different unique personalities that all have their own appearance, gender, voice, etc. specifically associated with them.  Here's what i'm still undecided on and looking for some community advice:

1) Do my character's personalities know about each other?

2) I like the concept of uncontrollable triggers bringing out specific personalities.  Ex: If my character gets drunk, Personality B comes out.  If my character gets too bloodied in battle, Personality E comes out.  If I succeed on an insight check against a creature being deceptive, Personality G comes out.  etc.  I'd like everyone's thoughts on versions of this or alternative ideas.

3) My character's current draft backstory (and background) has it as a urban bounty hunter assassin so I like the idea of the origin of the personalities being driving himself mad from staying in character too long to really get close to his targets that the different main identities he defaulted to started to become more real in his mind then just a disguise.  Another idea was that some deep guilt over each target he assassinated that he could have brought in alive triggers him to adopt that individual's appearance and personality as one of his own personas.

Finally, and most importantly, I do not want to make light of any real disorder that people face as far as Multiple Personality Disorder or Dissociative Identity Disorder.  I'm not trying to take a real world disease that afflicts some and make a fun game character off of the symptoms.  Any help on how to make this element of his personality be unique and not making light of those real disorders would be appreciated.

Thanks in advance!

1) They’re not really different people. They’re not “personalities,” they’re personae. You’re still the same changeling underneath, you’re just in a different costume. The costume absolutely can have a very significant impact on personality, such that you’re functionally a different person as far as other people are concerned, but you’re still the same person “on the inside.”

2) I would shy away from “uncontrollable triggers” per se. But shapeshifting as an expression of temporary emotion could be fun. It doesn’t need to be deliberate or even something the character is consciously aware of. For example, maybe one of my personae is a blacksmith, and I see someone doing a really dumb blacksmithing mistake. Because my forms are masks, I always know how to blacksmith, not just when I look like my blacksmith. I start to yell at the person, but as I get more and more emotional I unconsciously shift into blacksmith shape because it’s appropriate to the situation.

3) This one has far less to do with “how changelings work” and more with “how your character’s particular pathology interacts with the fact that they can shapeshift.” I think it sounds interesting, but it might be difficult to play in a satisfying way. It’s the sort of thing that sounds like it would work better for an NPC than a player character.

Further Addendum, I've decided to go with 12 alternate personalities (the 13th being the actual Changeling's personality) based on the 12 major archetypes for good diversity amongst the personalities... they would be as follows:

The Innocent (Goal: to be happy)
The Regular Joe (Goal: to belong)
The Hero (Goal: expert mastery in a way that improves the world)
The Caregiver (Goal: to protect and care for others)
The Explorer (Goal: the freedom to find out who I am through exploration of the world)
The Rebel (Goal: to overturn what isn't working)
The Lover (Goal: intimacy and experience)
The Creator (Goal: to realize a vision)
The Jester (Goal: to have a great time and lighten up the world)
The Sage (Goal: to use intelligence and analysis to understand the world)
The Magician (Goal: to make dreams come true)
The Ruler (Goal: to a create a prosperous community)

Quote from SagaTympana >>

1) They’re not really different people. They’re not “personalities,” they’re personae. You’re still the same changeling underneath, you’re just in a different costume. The costume absolutely can have a very significant impact on personality, such that you’re functionally a different person as far as other people are concerned, but you’re still the same person “on the inside.”

 

 Thank you for the feedback!  For this specific point I wanted to clarify that I understand that the Changeling race doesn't morph into different personalities, just appearances.  What I'm working on building is more of a character that does have a multiple personality situation and if you mix that with the fact their physiology is that of a changeling, their body can subconsciously shift into the perceived appearance of that personality.

Despite it's obvious contradiction to my last point, I'm essentially looking for if a human in our society today that had to deal with multiple personality disorder happen to wake up tomorrow as a changeling and their subconscious mind used it's physiology to match switches in active personalities.

I'm a DM in other campaigns so the actual play style of changing personality and voice is something I have a pretty good handle on as I do it regularly enough hopping from NPC to NPC.

Be cautious regarding roleplay of real world disorders.

Instead of portraying it as a disassociated identity affliction, try considering it as extreme method-acting. Triggers being more like adapting reflexively from habitual use rather than total autonomy outside the character's control. Refuse to "break character" as an artiste regarding  a matter of pride rather than being trapped in a state of confusing limbo or half-awareness while another personality asserts itself.

Optics is everything. It's not easy to pass off a real world affliction that causes suffering to many as roleplay for entertainment value.

Quote from EricHVela >>

Be cautious regarding roleplay of real world disorders.

Instead of portraying it as a disassociated identity affliction, try considering it as extreme method-acting. Triggers being more like adapting reflexively from habitual use rather than total autonomy outside the character's control. Refuse to "break character" as an artiste regarding  a matter of pride rather than being trapped in a state of confusing limbo or half-awareness while another personality asserts itself.

Optics is everything. It's not easy to pass off a real world affliction that causes suffering to many as roleplay for entertainment value.

 This is definitely one good idea.

I may not have worded my original post as well as I'd have liked, the intent of what i'm looking for is some alternative story ideas to the origins of each persona.  Specific to my 3rd question.  What I basically am looking for is I don't just want "I'm a changeling and these are my different main personas I use"... I want there to be more depth and history to each one.  I want them to feel like independent personalities and not just different masks.

The Masks and Personas section of the Changeling race should be helpful

WGtE, ERFtLW

Basically, a Changeling may have a persona tied to specific skills / features, and always chooses to shift into that persona when using those abilities. Much like how a regular person would try to use associations and mnemonics to remember things, just a little more involved.