To open the door at the bottom of Deep Docks in Hollow Knight: Silksong, you need to use a "Simple Key." This door is locked behind a lava gap that requires the "Swift Step" ability to cross. The steps are:
- Obtain the Swift Step ability, which allows you to dash and jump across the lava gap in front of the door.
- Acquire a Simple Key. There are four Simple Keys in the game, which can be found or purchased in different locations such as Bone Bottom, Sinner’s Road, Songclave, and Sands of Karak.
- From the Deep Docks Bellway sign, head right into the "enemy rush" room and clear the enemies to open the path.
- Use Swift Step to dash and jump over the lava gap to reach the platform with the locked door.
- Use one Simple Key to unlock the door.
Behind this door is a sub-area with new enemies, platforming challenges, and valuable rewards such as Flintslate (a tool that adds fire damage) and a Craftmetal pickup to craft more tools. This door and area are optional but provide combat power and exploration opportunities.
