Caliburne ～Story of the Legendary sword～ is a boss-tier original composition by Project Grimoire, a five-person supergroup comprising Team Grimoire, Ice (Wilson Lam), Amaneko, Verdammt, and 悠久屋こてつ, that debuted in maimai ORANGE on March 5, 2015. It stands as the definitive climax track of its home version, demanding an unprecedented 1,000 music tickets to unlock (the highest single-song ticket cost in the series at that time). The song narrates the story of Rufu, the last heir of a clan sworn to seal magical weapons, as he reaches for the legendary sword Caliburne. Musically, it is a direct sequel to Brionac ～Lugh Lamhfhata～ from Rayark's Cytus, and later spawned its own sequel, Excalibur ～Revived resolution～, in maimai MiLK (with a fourth series entry, Arthur ～once Upon a Time～, existing outside any rhythm game). At a driving 190 BPM the track barrels forward for 2:23 before gradually decelerating in its closing measures, while the jacket and music video display the title simply as "Caliburne." The MASTER chart (level 14, designed by はっぴー) earned the community nickname "肩バーン" (shoulder burn) for its grueling three-quarter-time slide sequences that demand wide, whip-fast arm movements across all three lanes, a chart so physically demanding it became a meme among veteran players. The EXPERT chart (level 12+, designed by Jack vs mai-Star, originally credited as "合作だよ" before maimai DX PRiSM PLUS) is itself no small feat. Outside maimai, Caliburne crossed over into CHUNITHM STAR (February 2018), CHUNITHM SUPER STAR, and ONGEKI bright MEMORY (September 2022). An extended version incorporating Brionac motifs appears on the Grimoire of Emerald album and the maimai ALL PERFECT COLLECTiON soundtrack, while t+pazolite's despair remix features on the Garakuta Scramble! album.