At some point in Cult of the Lamb you'll need to get your hands on some Menticide Mushrooms. Here's where to find them.
While the overall goal in Cult of the Lamb is to slay heretics and build a following, along the way you'll receive little quests from friendly characters or from your followers themselves. Some fo these quests task players with finding certain items, either for the NPC's own personal use, for rituals, or to help build a range of decorations. Menticide Mushrooms are one such item, and used for a very specific Brainwashing Ritual.
Gathering 25 Menticide Mushrooms will allow you to perfom a ritual that puts your followers into a substance-induced trance, locking Faith to 100% for two days. Here's where to find some Menticide Mushrooms.
Where to Find Menticide Mushrooms in Cult of the Lamb
The primary place to begin farming Menticide Mushrooms is in Anura — the game's second level. As you move through the rooms, be on the look out for small clusters of red and white mushrooms, usually situated in the corners of rooms. Strike these down for a chance to harvest Menticide Mushrooms or some spores to plant your own.
To unlock the Brainwashing Ritual, you'll need to deliver enough Menticide Mushrooms to Sozo in Spore Grotto. This area is only unlocked once you've encountered some Mushroom-like worshippers out in the wilds of Anura.