There are four Simple Keys in Hollow Knight: Silksong, and they can be found in the following key locations:
- Bone Bottom — Purchase from Pebb's store for 500 Rosaries.
- Sinner's Road — Obtained by defeating the Roachkeeper enemy.
- Sands of Karak — Found on a pilgrim corpse sitting on the rightmost bench.
- Songclave (Choral Chambers) — Purchase from Jubilana's store after completing The Wandering Merchant quest for 650 Rosaries.
These Simple Keys can be used to unlock four locked doors in different areas:
- Bone Bottom: Unlocks a shortcut through the Wormways leading to the Chapel of the Wanderer.
- Deep Docks: Opens a shortcut to Far Fields and grants access to the Flintslate item.
- Sinner's Road: Unlocks the cage imprisoning the Green Prince to start his questline.
- High Halls: Opens a rosary vault room with multiple chests and a Rosary Cannon.
These keys and doors are significant as they open new areas and grant access to useful items and shortcuts in the game, making progression easier and more rewarding. The keys are scattered across the map and require varying degrees of exploration and combat to acquire.