Kagali is a former Demon Lord and president of the Moderate Harlequin Alliance, who had once been known as "Curse Lord" Kazaream (カザリーム). Seemingly killed by Leon Cromwell 200 years ago, Kazaream managed to survive by escaping with just his Astral Body and now occupies a Homunculus body in the shape of a female elf.

(Source: Tensei Shitara Slime Datta Ken Wiki)