Well he was stated to have destroyed multiple nations within seconds, and is more than capable of destroying all of Gransys if the Arisen fails to slay him. The Arisen in question is also a pretty casual lightning timer, and can also dodge meteors falling from the sky. So country-continental and MHS. Other than that, Grigori has the typical fire breath, alongside magic that nets him some pretty basic elemental manipulation, mainly fire, ice, and lightning, as well as being able to call down the aforementioned meteors and some AoE holy magic. The fun part come when a previous Dragon created Bitterblack Isle, which is a place beyond the Rift: the Rift in question being what connects each universe with each other, so he should also have limited dimensional manipulation to some extent.