To open the locked door in the Deep Docks area in Hollow Knight: Silksong, you need the Simple Key and the Swift Step ability.
- First, obtain the Swift Step ability, which is a dash-run that allows you to clear a lava gap in front of the door.
- The Simple Key is a single-use key. There are four in the game, and one can be bought early in the Bone Bottom area from a shop for 500 Rosary Beads.
- After you have the Swift Step and at least one Simple Key, return to the locked ornate door beyond the lava gap in Deep Docks. Use the Swift Step dash to cross the lava gap, then use the Simple Key to open the door.
- Opening the door reveals a sizeable sub-area with new enemies, platforming challenges, and rewards such as the Flintslate combat tool and Craftmetal for crafting.
The Deep Docks locked door is optional and not required for main story progression. The door unlocks a side area with additional content and challenges.
