Mutandis is an item from the Witchery mod. This item is used to mutate plants into other, random plants. This is the only way to obtain certain Witchery plants, like Spanish Moss, Rowan Saplings, Alder Saplings, and Hawthorn Saplings. Mutandis can be upgraded into Mutandis Extremis, and is also used in transmuting meat items into other meat items. In the Spirit World, Mutandis can be used on other plants to create Nether Warts. Using Mutandis on a Flower Pot that contains a Vanilla plant will change the contained plant to one of the other vanilla potable plants.
As of Witchery 0.21.0, custom plants added by other mods can be added to the mutation list through the config file.
This information pertains to an older version of the mod.