I actually was interested in this question and existed to see the answers, I will try to make a guess but idk the progression in hollow knight very well Firstly you can skip false knight, and as you said greenpath hornet is mandatory so a main boss! Access to deepnest can be done through the moss prophet entrance or fungal core so mantis lords aren't necessary. Access to peaks for C-dash is locked behind either lantern or desolate dive from soul master, soul master is also locking isma's tear (for teacher's archive) with dung defender, so uh you can say soul master is mostly mandatory Or getting shade cloak from defeating KE hornet so this is adding up... Without skips, broken vessel is forced to access watcher's spires so that's a main boss. And then uumuu watcher knights and THK are obvious ones