I don’t have verified, up-to-date information on a “Witches Crest” in Hollow Knight: Silksong.
If you mean a specific crest item, check the latest in-game questline, hidden area, or NPC reward tied to witches or a witch-themed region.
Search community guides, patch notes, and the current Silksong wiki for the exact item name and acquisition method.
If you want, I can help you find the most likely location or confirm whether this item is real, renamed, or from a mod.