Altar is the first area of the 13th Hierarchical City of Kagutsuchi. It stands atop the Novus Orbis Librarium branch within Kagutsuchi, and is named after its large Monolith. Mu-12 was reborn here on January 7, 2200.
Far atop Kagutsuchi's sky, Altar rests on the top of the NOL branch. Hazama used the Monolith to take the souls of the nearby soldiers to fuel it, making them the fuel for the smelting of Noel Vermillion into Mu-12. The plan was a success, and Mu was born after Hazama and Yuuki Terumi battled against Ragna the Bloodedge. Terumi killed Lambda-11 at this time, and she died next to the Altar itself. Ragna managed to defeat Terumi at the Altar for the first time. As a result of the Continuum Shift, Hazama and Terumi went through multiple shifts, also battling against: Jin Kisaragi; Rachel Alucard; Taokaka; Iron Tager; Carl Clover; Arakune; Litchi Faye-Ling; Bang Shishigami; Hakumen; Tsubaki Yayoi; Makoto Nanaya; Valkenhayn R. Hellsing; and Platinum the Trinity. In each shown battle, Hazama and Terumi were successful in smelting Mu.
The Altar was further reborn in both the Realm created by Noel, where she battled against the side of her soul that harbored Mu. With Rachel's assistance, she was successful. Within the Embryo, the Altar was created once again, and Hazama explained his wish as one of the chosen to Ragna within the space.
The stage itself is a wide, circular space with various runes. In the middle stands the pure black Monolith which the stage is named after. The sky is a sunset orange, with clouds encasing the stage itself. In the Adventus version, the Monolith is alight with blue lines and purple runes - above it rests a giant winged cocoon, and on the front of the Monolith is the emblem for the Azure Grimoire.
- BlazBlue: Continuum Shift, Story Mode, True Ending
- BlazBlue: Continuum Shift Extend, Arcade Mode
- BlazBlue: Central Fiction, Story Mode, Episode 008, Chapter 062