You have become a Grim Reaper—the personification of death and the afterlife itself.
As a Grim Reaper, you possess a deep connection and understanding of the concept of death. Composed of its very essence, you can utilize the power of death magic better than any mortal or undead could ever imagine, capable of wielding death in all its manifestations and forms.
As a part of the natural order of things, your use of necromancy does not disrupt the cycle of life and death. The power of true resurrection is also yours to wield.
You no longer need to cut the line of death or stab the point of death to activate the instant kill effect of the mystic eye. As Death itself, simply hitting an opponent with the intent to kill is enough to take their life; even immortal beings can be killed by your touch as you forcefully impose the concept of death upon your enemies to ensure their demise.
Your Soul Garden now becomes a fully developed afterlife. Whatever form it takes—whether a place where souls permanently stay after death like heaven and hell, or a cycle of reincarnation—is completely up to your choosing. It can be changed at a moment's notice at your whim.
Regardless of whether the soul stays in the afterlife or goes on to reincarnation, as long as you ensure that the cycle of life and death continues and the soul of the dead is taken care of, not dissipating into oblivion, you will continually become stronger.