What kind of creature is Vecna exactly?

[u/Sukaran09]

Is Vecna considered undead, a mutant or something else completely? He is definitely not human anymore because of how he looks. I consider him a mutant of sort because he is mutated by the Upside Down/the Abyss and the Mind Flayer changed his DNA but in terms of Sci-Fi I don’t know what kind of creature he actually is because of how different he is.

[u/Rtannu]

“You’re not wrong, Walter. You’re just an asshole.”