Hm, this sentence sounds a little weird. It's mostly because of a missing article but the word "surely" sounds off in modern times too. I do realize this is an alternate world though, so if the dialogue is intentionally written like that for this character then more power to you~! Assuming it was intentional I'd change this to:
"This big crystal in the center is surely the heart."
its unfortunate not many people appreciate the rpg maker programs.
kids these days who play games only are about cod and w/e other shooter they own :/
i grew up with Nintendo and Genesis so stuff like this is amazing and beautiful to me :3