aha, uhhh, sea hitler race
lol
so theres not alot different between the violet bloods and fuscias besides ancestory, the violet bloods i belive decended from a purple blood because of the anger we see eridan and cronus have when they dont get their way, and the similarity to blood color. the other thing i can say is that violet bloods are actually still evolving from land to sea, eridan can live out of water for his entire life, whilst we dont know alot about what happends to fef when she stays out this long. the still evolving theory is merely speculation for why they have less fins than fuscias do. what may have happend is that purple bloods had to escape to the water, and due to their violent nature they still wanted to murder even in the sea so im thinking they took rust bloods with them, making group A and B. group A are the ones who became the land loving ones and group B are the ones who lived under the sea and evolved.
regarding anatomy and strenghth they dont actually have much, the thing that makes them well equiped and more tolerating to attacks is the slightly bigger bones, the bones are still small but they are much stronger. regarding strenghth they also have alot of muscle as the fuscias do, but its more harder to gain strenghth than other blood castes do. this is due to the fact that purple blood were already strong and could stay in water easily, they had no need to exersize when they are living in the water with muscle already, and so it became harder to gain strength.
the reproduction allows actually alot more violet bloods, of course violet bloods being rare due to age, violet bloods grow till about a few centuries, less than the fuscia, but again the purple bloods didnt have a need to change that much in the water, so violet bloods mature alot faster and so theres alot more violet bloods.
ill try adding more at another time once i can.