A Crimson Noble is a being of supernatural abilities, and is the Wild Arms series' take on vampires.
The Crimson Noble of Wild Arms 2 was Marivel Armitage
In Wild ARMs 4, Scythe, a member of Brionac, believed himself to be a Crimson Noble. However, as stated by Lambda, Scythe was a hemophile who had an urge to drink blood, eventually believing himself to be a Crimson Noble. And by sipping Belial's blood, he gained the temporary ability to control time and space.