- "If this babe born just two or three hours ago is the chosen one, he's the only success. This fella here is what you get after taking the chosen ones and doing millions of experiments. So, you think as a brat still in diapers, you're fit to face off against some one so far beyond your level?You'll never be him. Not in a million years!"
- ―Left HandScenes From An Unholy War|[src]]]
These are Chosen Ones by the Sacred Ancestor and given some of his power who along with experimentation had their genes manipulated combining the Human genes of light and the Noble genes of darkness with a result that the Sacred Ancestor has recognized as a success.
There have been many chosen ones through out the series, and these individuals were given some of his power and if they showed potential then they were further tested beyond this by seeing if they could help further the evolution of man kind and Noble species. There has only been one confirmed success. How ever Lawrence Valcua was also once told he was a success as well. Why this changed isn't clear but it seems it has something to do with more than just evolution, experimentation, ability, and power. The best educated guess would be mental fortitude and aversion from jealousy and cruelty. It may also have something to do with the Akashic Record.
The Sacred Ancestor has been traveling the world coming to select areas where he asks for the strongest and the brightest of the village, town, or other group. Usually consisting of the top five individuals. He from there chooses who will become chosen ones or just aid him in experimentation such as Fisher Lagoon's DNA he took from him. In Twin Shadowed Knight it shows that these individuals in order to find the potential needed they go under millions of tests, everything from regeneration properties, mental fortitude, strong will, fortified genetic structure, special powers and abilities, and resistance or immunities to diseases and death by physical, biological, chemical, etc. means. To be a success one must be able to also resist or have a high resistance to feeding on blood in general as seen with Baron Byron Balazs once their power is fully realized.
Powers and Abilities
All chosen ones have shown exceptional ability beyond most Greater Nobles. This is further explained in Chosen One Powers. Those considered a success out pace even chosen ones which is further explained in Success Powers
Almost all chosen ones have Mimic, Bestowed Power From Sacred Ancestor, The Night, Reality Warping, or other special abilities that put them in a league of their own. D and Valcua have shown to gain more powers as they go along and higher resistance. D in particular surpasses all others in this area. They also have all the special privileges of being The Sacred Ancestor's Direct Bloodline.
Left Hand being apart of D and having power rivaling him can be considered one of the success possibly. Twin D has all the powers of D so there is no reason to believe he can't be considered a success. Even when talking about "D" he himself would be remiss in separating himself from his brother even in this regard.