When Wes caught up with Hollow Knight creators Team Cherry last year, they mentioned Boneforest—a lava-filled zone that was cut near the end of the game's development. The dev's Ari Gibson has spoken more about the ill-fated area in an interview with Game Informer.
"We removed one large area from the game, the Boneforest," Gibson tells GI. "It was a huge later-game area filled with lava. Cutting it was tough at the time. It seemed so cool! But it was totally the right thing to do. William and I were already slammed with all the other enormous areas to build, and they all would have suffered for Boneforest’s inclusion."
In conversation with Wes, Gibson and teammate William Pellen explained they originally planned to have other levels below the Boneforest—which Gibson didn't approve of. They eventually moved the zone south, before ultimately axing it entirely.
Both Gibson and Pellen seem certain this was the right decision, but it did look cool nevertheless:
It also turns out Deepnest was once much bigger than what now appears in-game. "We also significantly reduced the size of Deepnest, which seems unbelievable, given how huge it ended up being, but most players would thank us for that decision," Gibson tells GI. "Too long in Deepnest isn’t good for anyone!"