In Hollow Knight: Silksong, "keys" refer to four simple keys used to open certain locked doors. They also include a few other specialized keys that allow players to pick locks and access new regions - for example, unique keys used in an area known as The Slab.
Keys
Locations on Pharloom
1
Architect's Key
This key can be bought from Twelfth Architect for 110 Rosaries, but first you have to collect 25 Tools.
2Bellhome Key
To get this key complete all donation wishes in Bellhart (Restoration of Bellhart and Bellhart's Glory) then talk to Pavo. It grants you an access to you own house - Bellhome.
3Diving Bell Key
4Key of Apostate
5Key of Heretic
The key will be dropped by the last of the defeated enemies in the room you jump into from above.
6Key of Indolent
7Simple Key (Mosslands, Pebb)
This key can be bought from Pebb (Mosslands) for 500 rosaries.
8Simple Key (Sands of Karak)
9Simple Key (Sinner's Road)
10Simple Key (Songclave, Jubilana)
This key can be bought from Jubilana for 650 Rosaries. To be able to do this you have to complete The Wandering Merchant wish.
11Surgeon's Key
12White Key
Unlocks the Locked Elevator (White Key) and grants access to the Citadel's Whiteward.
