Grievous Lady entered the maimai series as part of DX Splash through a crossover with lowiro's Arcaea, bringing one of that mobile game's most formidable boss tracks to the arcade. The piece is a collaborative effort between Team Grimoire and Laur, two composers whose prior maimai contributions include TiamaT:F minor (Team Grimoire) and Mutation (Laur), and delivers a relentless hardcore assault at 210 BPM built around driving synth work, hammering percussion, and a single recurring vocal sample of the word "Rezonated." In Arcaea, the song served as the final hidden boss of the main-story pack Vicious Labyrinth, gated behind a special unlock mechanic known internally as an "Anomaly" encounter. Its maimai arrival was tied to the Arcaea Area (Arcaeaちほー), a limited-time collaboration event in Splash that ran from January 8 to March 3, 2021, during which players could unlock the track by accumulating 273 km of in-game distance. After the event closed, Grievous Lady became permanently available from March 4, 2021 onward, and later rolled out to Asian and Chinese region releases through their own localized events. The MASTER chart, designed under the pseudonym Anomaly Labyrinth, weaves the source game's identity into its structure: the name itself compounds "Anomaly" (Arcaea's term for hidden boss encounters) with "Vicious Labyrinth." Its most talked-about moment occurs during the "Rezonated" buildup before the drop, where the note stream briefly reverses direction, translating the original Arcaea chart's optical-illusion gimmick into maimai's five-lane format.