I’m just gonna explain every single one of them:
1-4. Bought from Sly in Dirtmouth (easy enough)
5. Defeat Brooding Mawlek In Forgotten Crossroads.
6. In Bretta’s house.
7. The right side of the Queen’s Station.
8. Found behind a wall in the Hive (requires for you to bait a Hive Guardian into breaking the wall)
9. The Grey Mourner quest.
10. From second crystal guardian encounter.
11. Given by Grubfather.
12. Given by the Seer.
13. In the Stone Sanctuary in Greenpath (lantern needed)
14. Area under False Knight where the Goams are.
15. In the Royal Waterways (Go left upon entering from the City of Tears)
16. (Quite easy to miss) the mask shard located in Deepnest near the Mantis Lords, requires for you to go through the Fungal Core area in which you will fight a bunch of mushrooms.
Original Link – Continuation of discussion