Gauma

Age: >5000 years
Hair: salmon pink
Eye Color: emerald green
Affiliation: Kaiju Eugenicists (formerly), Dynazenon (currently)
Origin: China, later transported to the Sakuragaoka museum in Japan

Gauma was a former Kaiju user affiliated with the Kaiju Eugenicists but defected from them and fights against their Kaiju using Dynazenon.

Near the end of the series, Gauma was revealed to be the Chinese mummy that appeared in episode 18 of Gridman the Hyper Agent, referred to as the Mummy from 5000 Years Ago according to printed materials, such as the Ultra Tokusatsu Perfect Mook.
(Source: Gridman Wiki, Ultraman Wiki)