Wasp Mountain

Overview
Wasp Mountain was a sidequest released for Hollow Knight: Silksong on October 1, 2022 to refresh the game. It has been hailed by critics as one of the hardest and best questlines in gaming history, citing the mountain's treacherous platforming, the unforgiving enemies, and the deadly, horrifying final boss. It was originally planned to be a DLC, but Team Cherry's Ari Gibson made it a sidequest 5 weeks before the launch.

Beginning the quest
To begin the quest, head over to the Lace boss arena in the Boondocks. You will see a strange-looking ladder right behind you. This ladder will not appear before you step into the arena (after beating Lace.) Head up the ladder. You will find a chest. Open it to reveal the loot: Seth's Tear. With Seth's Tear, jump into the arena's lava. Under the lava is a tramway. It requires no tram pass. Take the tramway to the Wasp Mountain.

Subo Village
Subo Village is the first location you'll be greeted with. It contains four NPCs: Hoarder, Beartooth, Stinger, and Uba. Hoarder is a young bug who sells various wares. Beartooth is an old warrior who offers trials. Stinger is a cowardly bug who has no dialogue. Uba is the quest giver. He commands you to find the Mountain Nail.

The Mountain Nail
Go upwards along the marked path. You'll see a sign that reads "Here be Death." You'll also see a pit. Jump into the pit, then fend off the Stingbeasts that emerge. To your right is a platforming section. Complete it. Then three Stingbeasts and one Sting Warrior spawn. The doors around the arena lock. Use the Daround the arena to outwit them. After that, go upwards to find a Bench. The upwards path splits into two paths. Along one of the paths is Cornifer's grave. Along the other is a deadly miniboss called the Sting Master. Beat him, and he'll drop the Mountain Nail. The ground splits open to send you straight back to Subo Village.

The Dream World
Use the Mountain Nail on Uba to be transported into the Dream World. Quickly, the Wasp King spawns along an arena with five platforms. Beat him, and Uba will then reward you with the Death String, which increases your needle damage threefold.