Hushrooms (5e Hazard)
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These mushrooms appear to be inside out, with their cap covered in the gills normally seen underneath it. When enough Hushrooms grow together in an area any noise is magically silenced as if under the effects of the silence spell. They can also be harvested to make food, which will provide the same nourishment as regular mushrooms, but the creature which consumes it will be silenced for 1d10 - Constitution modifier hours (Minimum 1).
You can render a hushroom into a contact poison. Harvesting a hushroom uses the Crafting and Harvesting rules in the Dungeon Master's Guide (p. 258). A creature subjected to hushroom poison must make a DC 13 Constitution saving throw. On a failed save, it is silenced as above.