Karnak was one of the Inhumans, a group of individuals whose ancestors where human beings that were experimented on by the Kree (another K). Each Inhuman went through a rite of passage when entering adulthood that involves being exposed to Terrigen Mists, a gas that grants them unique attributes and powers. Every Inhuman, that is, except for Karnak. His older brother Triton, had been turned aquatic from the mists, and so their parents did not want Karnak to go through it, afraid that something negative might happen to him. Instead, he studied martial arts and did gain a gift, the ability to see the weakness in anything, be it physical or tangible, such as a plan.
He was an important part of the Royal Family, and a strong advisor of Black Bolt’s. He obviously had a gifted mind for strategy and was able to help the Inhumans through many tough times. He also has the typical Inhuman metabolism, which apparently gives him heightened reflexes, as well as increased durability and strength.
In consulting with Marvel’s wikia, I learned some disturbing news. Apparently, in Inhumanity #1, which only came out a couple months ago, Karnak leapt from Avengers Tower and killed himself, being unable to fix his life. I am shocked and saddened by this news. He was always one of my favorite Inhumans, a group which always held my interest. I will mourn for you Karnak. Suicide was no way for you to go and I don’t think it is something that you will be brought back from. I was going to try Inhumanity this summer, but now, now I just don’t know.