A monolith (モノリス monorisu), also known as a tablet (タブレット taburetto) is a catalyst for a Kiln.
Monoliths can also perform functions of a Kiln, and, like the Blue Grimoire, they are clumps of magic element.
During BlazBlue: Continuum Shift story, Hazama installed a monolith at the top of the World Void Information Control Organization’s branch in the 13th Hierarchical City of Kagutsuchi; here, the monolith absorbed soul of every soldier, allowing it to be able to smelt Noel Vermillion once more so she could become Kusanagi – Mu-12.
Ragna the Bloodedge could feel its “pulse”, like that of a Kiln.
In story of BlazBlue: Chronophantasma, it was discovered that the jet black pillar (漆黒の柱 shikkoku no hashira) in the 5th Hierarchical City of Ibukido was a huge monolith created by Izanami with its base connected to the Kiln underground. This pillar collected souls from all over the world to open the Nemesis Horizon and to smelt the Embryo. Eventually, Jin Kisaragi and Hakumen destroyed its base, and Bang Shishigami nailed Phoenix Wing: Rettenjō into Kushinada’s Lynchpin, and launched it at the monolith, causing the overwhelmingly huge structure to sink into its foundations. Despite this, a sufficient number of souls had been gathered and Izanami was able to make Embryo out of Takemikazuchi.