nyarlathotep, the Black Pharaoh, seeks to enter the realm of Earth to rule over mankind. Unfortunately, he is prevented from doing so by a barrier that blocks eldritch deities from crossing over. To get around this, he breaks his soul up into thousands of pieces and seeds them into thousands unborn children. These kids become immortal avatars of Nyarlathotep called Nylanders, who do battle with each other over the centuries through one-on-one engagements to the death. When one is killed, the other "eats" the loser and gains their power and memories, absorbing them into themselves. When all pieces of the deity have joined, Nyarlathotep will become whole within one body and would be reborn on the mortal plane. In the end, there can be only one.
However, even though a Nylander can kill another of his kind and take his soul, he doesn't benefit personally. While he has gained the power and memories of the fallen, he is unable to gain access to any of it. The winner remains completely unchanged, making everyone on an even level when they do battle. This slows down the assembly process, stretching it out to centuries instead of a short period of time, and making it more difficult for the deity to unite its pieces.
What would be preventing these warriors from gaining the abilities of others after defeating them?