Red XIII is a ferocious beast with flaming red fur. Despite his bestial appearance, he is amazingly eloquent and fantastically intelligent - an astronomer, no less. His kind can live for hundreds of years. Conjecture: Red XIII is super-intelligent, a lives for hundreds of years, and currently resides with the Shinra Corporation (as a pet).
This information, coupled with his name, "Red XIII," make it seem that he is a genetic experiment of the Shinra Corporation - perhaps the thirteenth of his kind? This explanation accounts for his tattooed "serial number," intelligence, and unique appearance.
