In my GOTY list last year (Hollow Knight #2 best game of 2017) I described the variety of zones in the game, describing one as “a dark and suffocating cave that is like a place made of literal nightmares.” I really like Deepnest, it adds a ton to the game. Yeah everyone is bugs but up to that point the art style makes everything pretty cutesy and charming. Then you get to Deepnest and no, some bugs are horrifying even to other bugs.
As a dude who really doesn’t like spiders, I loathed my time in Deepnest (but in the best possible way). One thing I really liked about it is that, after the point where you find the hotspring and bench, it legitimately feels like you’re trapped in there. I really, really wanted to be back in town or in any other area of the game but the only way to make that happen was to continue through Deepnest and face my fears. When I finally made my way out, I left it for awhile. I still have to go back there and get the tram pass, but that tension of being trapped in an area that I love/hated and finally getting out and having the choice on whether or not to go back in (at least until I exhaust all other options) is very, very memorable. Also - thank Christ I was pretty powered up and had the lantern before I went in there or else it might honestly have been too much for me.
deepnest and the royal waterways both do a really good job of making it creepy by changing the way death works. you’ve spent however many hours safe in the knowledge that you knock a bug down and it stays down. every one of them left a corpse but there was no reason to pay it any mind. then suddenly the corpses get back up and pull out some body horror as they do it, and you’re second-guessing everything. it’s some chef kiss enemy design.
edit: actually i remembered that in greenpath some enemies explode, so you are primed for corpses to hurt you to some degree, but the beautiful horror of deepnest is that the enemies that get back up are the same basic-ass bugs you’ve been fighting since the crossroads, who you have no reason to suspect