Bitter Herba Mystica (Japanese: ひでん：にがスパイスSecret: Bitter Spice) is a type of ingredient introduced in Generation IX. It is one of the five Herba Mystica.
In Decisive! The Battle in the Sky!!, Violet and Arven discovered the Bitter Herba Mystica after defeating TitanBombirdier. Arven made some sandwiches out of it, sharing them amongst himself, his Mabosstiff, Violet, and Mireia, a Musician who had helped them against Bombirdier. The power of the Bitter Herba Mystica allowed Mabosstiff to recover a little more, much to Arven's relief. When Miraidon ate one of the sandwiches, it gained a power-up, with Professor Turo contacting Violet to specify that Miraidon had regained its ability to swim.
