Why Kai'sa is not insane.
Kai'sa's interactions are out, and while we wait for her story to confirm or ignore some of our Void-related questions, I wanna make a post about the Void, what we know about it, and how it pertains to her voice.
Malzahar and Kassadin offer very little to our knowledge of the Void: from Malzahar, we know that some give in to the supposed inevitability of the crossing-over and become servants-- if not slaves-- to the Void itself. Malzahar actually leads a cult of such people. From Kassadin and other unnamed "Preservers", we know that there's an opposing group which has seen these horrors and fights to prevent the downfall of the entire planet. Though it's not stated in their lore, by their own actions the Targonians are all also members of this opposing group.
Current lore actually has nothing stating that the Void drives people insane unless you consider giving in to be insanity-- which I don't. Becoming subservient to something or someone because it's more powerful than you is a part of basic human nature. The powerful lead. And to that end it's only Malzahar and Kassadin's voices that are distorted, their minds have remained largely intact.
That said, for Kai'sa it's not the Void that would drive her mad--- it's the complete lack of human interaction. We don't even have any indication that the Void has invaded her mind, considering the lack of distortion in her voice. But even a grittier-than-average person would lose their sanity with time in isolation. My theory is that the armor she's clad in is the very thing preventing her descent into madness.
Her symbiotic relationship with the creature on her body is completely obligatory-- meaning neither can live without the other. So it stands to reason that the creature would do all it can to dull her sense of fear in the face of the overwhelming danger the Void poses even to void-born creatures. It needs her sane so she can hunt and keep them both alive. But an unintended side effect of dulling her fear is that her ability to feel and express all of her emotions has been nearly erased.
This is why her lines sound.... dull. The most emotion she shows is happiness when she's eating-- eating honeyfruit to be exact. And that makes perfect sense. The sole desire of the creature on her skin is to hunt and eat in order to evolve. Even it would express delight at the extremely nutritious meal. Similarly, her anger is noticeable-- however slight-- when attacking another Voidborn. To her, they're evil. And to it, they're competition.
It's a miracle she still maintains her desire to protect humanity despite her situation doing everything it can to turn her into nothing more than a savage beast. The fact she's boring because of it is far more fascinating to me than how such a character is normally written. And there are two examples of the norm from this game: Swain overpowering the demon inside him to make use of its power while completely maintaining his sanity, the reverse of Warwick completely losing himself to his animalistic instincts-- his is even combined with the trope of keeping "just enough" humanity to only attack villains.
The third generic way to write such a character is to do exactly what some on the boards have suggested: have the character act as if torn between the two halves. Riot's actually done good ignoring this trope once already via Kayn. Whether he beats Rhaast or Rhaast beats him, the victor is still a villain. And while they're together the banter isn't torn, merely competitive.
What they've done with Kai'sa's personality is a unique and realistic approach to this particular kind of duality, and they know it. She isn't boring for the sake of being a dull character. She's overly calm for the sake of being one that stands out.
Important Edit: The first draft, I left out that I think the symbiont is specifically producing some kind of natural dampener to curb her fear. Such a thing wouldn't be strictly tied to a single emotion, so it would effect the way she feels and exhibits most emotion. Specifically when she's eating honeyfruit, the symbiont may halt production of the dampener because it is happy, allowing her to express her happiness as well. Likewise, when fighting a Voidborn competitor the symbiont may produce excessive amounts of adrenaline without halting production of the dampener, causing her to exhibit muted anger.
I know this is a little biology heavy for a game where most physical traits are explained with magic, but seeing as she's this game's take on an alien hybrid rather than a demonic, magical, or god-infused one, I believe this explanation fits best.
