Silksong walkthrough explains how to reach The Cradle and defeat the final bosses of Act 2, and how to start Act 3.

There are basically two ways to obtain a map of Hollow Knight: Silksong, and they depend on the region you are in.

This Void Mass is hanging above a pit of spikes in Shellwood. Since the mass could attack with tentacles or blasts, shoot at it from a safe distance, one platform before the one Hornet is standing on, ...