The Black Forest's Treasure is an item in the Rosenkreuzstilette series. It's an item that allows Lilli and Strudel to use their power to ram enemy targets as a means of fighting alongside their partners Spiritia Rosenberg and Freudia Neuwahl.According to Lilli, the Black Forest's Treasure is a sacred treasure of the fairies that they have been watching over for a long time. If Tia happens to stumble upon it in Trauare Wrede's stage in the first game, she suggests that they take it back with them, and Lilli agrees, saying that they have to stop the coup launched by RKS against the Empire, especially for the ones waiting for them in the other forest. When Lilli suggests to borrow some of its power, she says that their ancestors will forgive them with the situation they're in at that point, and Tia, thanking her for volunteering to fight with her, is glad that they're both in it together. Similarly, Ruu will also borrow some power from a treasure found in Liebea Palesch's stage in Rosenkreuzstilette Freudenstachel that is similar to the one found by Tia and Lilli. She mentions that there are 77 treasures scattered across the world and that the actual number is 78. Implying on her playful nature, the treasure found by Freu and Ruu probably won't be returned until they bring Tia back to the others at RKS from captivity by the hands of the Schwarzkreuz (and Iris, her real captor).
In the first game, the Black Forest's Treasure is colored green, while the one in Freudenstachel is colored blue.