Help me find this novel about propably royalroad novel with mc that became insane after long time in a dungeon.

Sorry for bad description, its all I remeber,

Best i can say is that its not madman apocalypse

Portal dungeon litrpg system apocalypse happens. Mc accudentally falls into one of such portals, he then throught some abilities and perks gets almost immortal, but somehow does not get out of portal, instead stays there for long enought to get insane, and starts to hear his plushie talking to his and giving him advices,

it didnt became alive or sentient, its his hallucination, his common sense kind of projected on plushie, its a way for him to stay insane to not break completly, his rationality saved in form of insanity, hallucinating that his plushie gives him rational advices.

Then he also gets very strong, like out of scale, and when finally gets out of portal, he is seen as murderer, maybe murdered some people, strong and mentally unstable.

Thanks for help

Ps thinking that madman apocalypse front image is what keep reminding me of that novel, maybe there was no plushie? A false memory about this novel caused by madman apocalypse, I am not sure but its possible there was no plushie, just soke type of hallucination of someone, maybe hallucination of plushie, mc friend, different verison of himself, or per he had

I would like to write something thst would narrow it down, but with how long I was searching for it everywhere, my paranoia starts to kick and I start to overthink if I even read it on royalroad, or scribblehub or webnovel or somewhere else.