Firstly, if you want to accomplish this, you’ll need to cook the recipe. You need one Cursed Msuhroom + Sun Caroway as seasoning. Mushrooms you can get at the Keep, and Sun Caroway spawns rarely on Sandfall island. This gives you a recipe with insanity 2. However, if you eat this recipe, then enter the keep (which gives insanity +1), you will get insanity 3.
Insanity 3 is the highest achievable insanity so far, as insanity 5 (given by the Keep secret and the dark sea entrance) kills you near instantly.
As for auditory hallucinations, I got no recordings, but there were the usual whispers, door opening sounds, etc, but I also swear I heard, at one point, (you can see I’m on my boat) white eyes below me. I freaked out and looked around but there was nothing there. Didn’t say White eyes was near the island in the news either.
This seems like a weird way to encourage running Warding if you decide to have Insanity for lengthened periods of time, since god those blinding effects are gonna be annoying as hell.
I should mention that the frequency of screen-changing events (including insanity 1 effects like darkening the screen) is quite fast. You barely get a moment of normalcy.
i once chased a pirate ship near the edge of the map then it stopped, and i went past it and as i was about to turn around i got hit by insanity 5 in the dark sea