Born ages ago during a time that wasn't recorded for the History Books, Isaac and Rivi were born and lived for 16 years until their lives were cut short. Even in life, Death had held a close eye on them and with the true awakening of Soul Edge, Death preserved their souls and bodies, reuniting them together to reclaim the tortured souls stolen by the Cursed Blade. With each rebirth of Soul Edge's terror, Isaac and Rivi awoke to chase down any signs of the evil seeds, and Soulcalibur, and free the trapped souls from within.
Of the two, Isaac is the most solemn. He rarely smiles or talks. Isaac is generally a grim and stony-faced person, but also finds himself becoming annoyed with living people. Rivi, on the other hand, is incredibly extroverted and spontaneous. While he completes the missions he is assigned, he makes sure he has incredible amounts of fun while doing it. He finds humans to be fascinating and exciting; he interacts with them as much as possible.
Isaac and Rivi are identical in physical characteristics, and although Rivi weighs more, it is not visible. They both have light brown skin and impossibly vibrant and rich green eyes. They sport matching hair styles in each game they appear, and a matching two player costume until Soulcalibur V. In Soulcalibur III-IV, their hair is bright red. In Soulcalibur V, is dark, and their skin darker as well. They are on the slender side, but lean.
Isaac's weapon is a large Scythe, while Rivi uses dual short blades. Isaac's scythe is Abyss/Zasalamel's Irkalla. It is his starting weapon, although during story mode he uses a different scythe that is more basic looking. Rivi's blades are called Kagekiri. They are direct from Death himself, and are the sharpest blades in the universe; they can even cut through shadow.
Isaac takes up the mantle of Death incarnate, granting him dark wings and unimagineable abilities. His weapon is his whole body. Rivi continues to use Kagekiri.
Soul Calibur IV
This is the cage that the brothers initially woke up in, during the events of Soul Calibur IV
Soul Calibur V
Outta the way!
You're in my way!
You wanna die that badly?
I could never lose to the likes of you!
You deserved that!
Stay there and die!
You shouldn't have trifled with me!
Feel the pain!
I definitely won't lose! - Taunt
You think you can handle this?! - Taunt
That was a mistake.
Time to die.
Know your place.
Making me waste my energy.
See? that's what you get
I'll gladly lend a hand if you want to die!
That was truly absurd.
Why are you shaking?
Get out of my way!
You should die.
Oh, amazing. How did you expect to win?
Why don't you hurry up and disappear?
I have no interest in speaking with the dead.
I suggest you run away, quickly.
You want me to hurt you some more?
They are Identical Twin Brothers of each other.
They are agents/apprentices of Death.
Both of their names are Hebrew, however, Rivi's name is traditionally used for girls.
Soul Calibur IV
Soul Calibur V
"Twisted Nerve" (Whistle Version) by Bernard Herrmann (Originally from the film Twisted Nerve) is Isaac's Theme
Rivi's theme is "U.N. Owen was her?" - TouHou
Isaac's Theme is