How to portray a character slipping into insanity over time?

Question

The deuteragonist of my trilogy, The Ragnarǫk Sequence is heavily implied to be Jeanne d'Arc (whose characterisation takes many cues from Artoria Pendragon) and serves as the protagonist's moral compass, criticising him for his less than heroic acts.

The series suggests that the deuteragonist is even more messed up than the protagonist and has Major Depressive Disorder, but hides it better (which says a lot, given that the protagonist suffers from severe cases of Borderline Personality Disorder, Body Dysmorphic Disorder and sex addiction). Such mental instability stems from the trauma of the Hundred Years War, struggling to conform to modern society's values where religion is outright mocked, everyone she knows being dead and having no human contact for over six centuries.

Things get worse when the deuteragonist learns that the various visions of Angels and Saints she had in life were attempts by an aeons-old, serpentine monstrosity with omnicidal tendencies called Jǫrmungandr to manipulate her into freeing it. This revelation is a crucial factor in making the deuteragonist abandon her religious views, as he comes to believe that she died for a lie and another is when Jǫrmungandr's "father"/"messager", Loki reveals that he killed and masqueraded as a priest giving her emotional support to destroy her sanity and render the protagonist susceptible to influence from Jǫrmungandr.

All of this insanity ends with the deuteragonist masturbating to a memory of the protagonist having sex with his former love interest, showing that she has hit rock bottom and leaving her wanting to commit suicide. And yes, it's as bad as it sounds.

The problem is that I want to write in a manner where the deuteragonist's sanity slippage occurs in a gradual and believable fashion, rather than some contrived, implausible way.

How should I accomplish this?

Answer 1

I say start off by having her try and hide her feelings, but throw little hints about how she truly feels as her mask slowly slips off. From there start showing her inner feelings on the outside over time and have those around her act like she is going insane more so if she lets slip about her last life. It becomes a case of not insane, but everyone comes to believe she is and it slowly wears away at her sanity. As this happens you can have her Depressive Disorder show more and even throw in her going from her mask to depression in public like her suddenly crying or going into a zombie like state in public.

I agree with one of the other answers change the type of language she uses as she gets more and more insane. Maybe even have her slip in and out of speaking like she did in her last life and throw in some swears in depending on the situation.

Follow it by having her lash out those around her as her sanity gets pushed. As those around her try and help have her start doubting her own sanity and if she is really Jeanne d'Arc as those around her start treating her differently. As she starts to have trouble distinguishing from what is real and what is false have her start doubting everything eventually deteriorating at her own morals and she does or considers things she normally wouldn't to try to gain some form of momentary peace from what is happening. She will later regret these things after she calms down and her reasoning comes back which makes her fall further and further into insanity as she feels that what she did was wrong, but also ok with it since she is that far gone. I think the bit where you said she is masturbating to a memory of the protagonist having sex with his former love interest fits well here. She knows it is wrong, but at the same time kind of likes letting go and have insanity take it's hold and make her forget about everything.

Answer 2

Look at "The Yellow Wallpaper" by Charlotte Perkins Gilman. It is the classic short story of a narrator's descent into madness, caused by post-partum depression and male oppression at a time when women were considered inferior.

Read Mark Vonnegut's “The Eden Express,” about "his descent into schizophrenic madness in a counter‐culture wilderness commune."

The first gives an example of a narrator not knowing she is going mad. The second has an astute author narrating his sudden descent into schizophrenia.

Answer 3

I don't know if this will help you or not, but here are some insights I've picked up from reading material that has tried to do (and in some cases done it by accident) what you are trying to do. Let's start with real life insanity that led to incredible literary work;

Phillip K Dick.

This is a man who struggled his entire life to get out of what he thought was a low form of the literary art - science fiction. The trouble was, he was too good at it and wasn't much good at anything else, including life. He was the epitome of a tortured writer. His last works were called the Valis Trilogy and ironically enough were the first of his books I ever read (I've now read most of them). This series of novels shows a steady descent into madness in a way that you really don't want to emulate - he was struggling with mental health at the time. You can actually see that in the writing, but the truth of the matter is that just reading the novels does give you some idea of how to approach your topic.

Secondly, I want to point out something I've noticed about good horror novels. No, this isn't an oxymoron; some of them are quite well constructed although I'm the first to admit that I'm generally not a fan. But, the writing style employed by the best in this genre is... well, basic. I wondered why at first. Most writers in this genre use simple sentences and simple words to describe some of the most horrific scenes imaginable like it was making coffee with breakfast and I didn't get it until I realised something; it's the simple language; the consignment of this horrific scene to the commonplace, that adds so much emotional horror to the scene itself. It's one thing to describe something as out of the ordinary and use the language that expresses that - the reader gets the sense of perspective and (IMO) it would act as a cushion to the nerves. Sure, it's horrific, but it's supposed to be, right? But expressing it in the language of the everyday, the commonplace; that makes it all the more divorced from what the reader is expecting from the tone and therefore actually enhances the horror.

So, my advice; start out with language that is appropriate to the sense of the uncommon for what your protagonist is experiencing, but dial back the intensity of the language as you write, while dialling up the intensity of the experiences being described. Basically you want to go from

Oh my God! The toaster caught on fire!

to;

That demon was calling me names again while it stopped me from taking the toast out of the toaster again. It's bad enough having to eat burnt toast without being insulted by a demon throwing little pieces of my brother at me while I'm trying to eat.

Just how quickly you get between these points depends on how much you want to draw it out, but basically the rule of thumb (as best I can express it) is that your language should get more commonplace as the content you describe gets more bizarre. This not only adds to the sense of horror, but also shows that your character is having more and more of a struggle to differentiate between the ordinary and the bizarre over time.

Answer 4

To portray insanity, my best technique would be from bad experiences. In one of my books, the character witnessed a kind of super natural event. He then tried to show it to the world, and was laughed at. I think that if your character was so fixed on proving he was right, he could come across as insane.