Original Kekkei Genkai
The term Kekkei Genkai refers to the "Blood Line Limits" or "Blood Line Traits" of specific clans. These traits are passed on genetically and give the one possessing these traits certain attributes.
Most possessing these traits hone their special abilities with rigorous training. However, those without the trait can never attain those skills, regardless of training regimen.
There are many different Kekkei Genkais, mostly unique to a specific clan.
There are no known "hybrids", or those that have two Kekkei Genkai.
Hard work, or training in certain jutsus alone is not a Kekkei Genkai, as it can be done by anyone (see Naruto->Rasengan, or Lee->Taijutsu)
Kekkei Genkai found in SL
There is a different concept behind it ... it should be a goal for people with many Orochimaru Kills to start anew, reborn with almost nothing, but the genetic traits from a Kekkei Genkai.
Some CAN be combined, but most cannot. For example, two different Doujutsus can not be combined.
You must have 80 Kills to be able to get a reset, you will see where when the time comes.
Currently there are the following traits in the game:
You will see general information about them each. More to come.
For those who have a Kekkei Genkai, there are additional KG titles in their bio: