Dream No More

The true ending. With Void Heart equipped, get the Hollow Knight low enough that Hornet binds it (as in Sealed Siblings), then Dream Nail the Hollow Knight to enter its mind and fight the Radiance - the real source of the Infection. A tough multi-phase finale: sword-beam barrages, spike floors and a final platforming climb through the light. Beat it and consume the light for the game's true ending. Needs only Void Heart - no Godmaster progress required.