(Disclaimer: I am not advocating for grave desecration or corpse desecration.)
Human remains can serve two different purposes in necromancy.
The first is that they can be used as altars or altar pieces, as they are imbued with Death's essence.
This is not necessarily due to energy. This can be thought of as an extension of sympathetic magic.
Corpses in general can also be thought of as "empty vessels" with room to house a new spirit.
The second is that they can be used as powerful taglocks for summoning the spirit that previously occupied the body.
Using the remains as a taglock can also provide a great deal of power over the spirit, but this is not an option with cremation.
There are a variety of ways to execute both approaches, ranging from ceremonially complex to divinely simple.
The corpses themselves can be considered blessed objects, mediums, vessels, or even idols.
Wendell and Tomekeeper describe the energy or essence of Death in both overlapping and contradictory ways.
Wendell describes Death's energy as an electrifying spiritual lifeforce, melancholy, shadowy, yet soft and deeply compassionate.
Tomekeeper and Wendell both describe death energy as destructive, absolute void, ineffably sublime, and fearsome.
Tomekeeper gives us the additional association with decay and sickness, as these signal the approach or passing of death.
These two approaches are not contradictions, and I think keeping both in mind can be helpful for a more holistic understanding.
However, running sickly, destructive energy through one's meridians and other lifeforce channels is described as courting disease.
Tomekeeper seems to believe that this is necessary for the sake of manipulating the energy directly.
If so, then emphasizing Wendell's healthier, more positive aspect of Death might be less dangerous in energy manipulation.
Wendell and Tomekeeper both acknowledge that instruments are less important than the spirituality of the necromancer.
In Wendell's case, this is both about one's relationship with Death and one's proficiency in channeling his energy.
In Tomekeeper's case, more emphasis is placed on the energy work and Death is more of an impersonal force.
Instruments have still been used historically, often overlapping with goetic tradition.
Summoning circles, robes, and ceremonial weapons like swords, spears, staves, and wands are mentioned in a lot of grimoires.
Some grimoires even give details about how to prepare a body in order to use it as a conduit for a spirit.
It might be best to consider most of these to have more value as religious ceremonial symbols than practical tools for magick.
Corpses, bones, and rotting flesh are saturated with death energy and can be used as focuses for that reason.
Everything else is probably mostly aesthetic.
Notably, this approach is very new to occultism.
Older necromancers believed that particular names, symbols, and rituals had their own inherent power.
Alongside specific times of day, astrological patterns, and times of the year, every detail was considered to be necessary.
Of course, the precise details still changed depending on the grimoire, the era, and the location.
Trance mediumship only developed in the 19th century with the Spiritualist movement.
It was still a part of older necromantic practices due to ritual trance, but this was only made central in Spiritualism.
With trance mediumship, traditional timing, instruments, sigils, words, and so on were no longer considered to be necessary.
"Energy work" also only recently became a major trend in Western occultism.
Wendell and Tomekeeper provide their own ways of seeking out Death's essence. These overlap heavily.
I also recommend a practice that is common to both Spiritualism and Greco-Roman Necromancy: the death trance.
Sleep is closely associated with death and spirit divination.
This is because deep sleep is often believed to be the closest the living can get to experiencing the peaceful rest of death.
Trance is a sleep-like state that is similarly associated with death.
Early Mesmerists had spontaneous spirit communications, leading to the practice being decried as "demonic."
From these early experiences, hypnotic trance induction became the foundation of Spiritualist "trance mediumship."
I consider this trance to be a mystical state of union with Death, and therefore a way to focus on his energy.
From this perspective, it is through the power of Death that trance mediumship works.
Tomekeeper and Wendell both describe Death as an energy, but they model this energy in slightly different ways.
For Tomekeeper, death energy is the opposite of life energy, associated with vitalism.
As such, it can be worked with like qi using tai chi, qigong, and reiki.
The difference is that it leads to sickness and death rather than health and longevity.
For Wendell, Death is a sentient and omnipresent force, like a metaphysical field similar to electromagnetism.
Death can be concentrated in certain places, much like electricity can, and Death himself can choose how this is done.
In both cases, the necromancer develops an awareness of Death so that they can channel him or cause ripples in his field.
A lot of the terms we use in magic are fuzzy and fluid; they can obscure rather than elucidate.
"Necromancy," strictly speaking, refers to a method of divination that relies on obtaining knowledge from the dead.
This is not necessarily confined to spirit divination, although that is the main implication of the word.
For example, it also applies to divination that uses corpses and bones, whether these remains are human or not.
Likewise, "necrolatry" can refer both to the veneration of the spirits of the dead and the worship of corpses as idols.
Necromancy and necrolatry can overlap, as they do in religions like Vodoun.
You can have necrolatry without necromancy, like how Catholics venerate the Saints without communicating with them.
You can also have necromancy without necrolatry, which is common in Spiritualism and European necromancy.
The worship of death itself is sometimes called "thanatolatry," which is a jumbled mess of a word compared to "death worship."
Due to the taboo nature of death worship leading to misconception, it has gained inaccurate connotations of suicide and murder.
Still, Death is venerated by a variety of incarcerated prisoners and violent gangs through Central and South America.
Some of them are murderers, but that's not because death worship itself promotes murder.
Also, "necromancy" is often confused with "nigromancy," which is a word for "black magic."
"Katabasis" is a descent or journey into the underworld.
In Spiritualism, mediums work primarily with two "places:" the Veil and the Spirit World.
The Veil, what Wendell calls The Valley, overlaps with the physical universe or the "corporeal realm."
Ghosts, apparitions, poltergeists, etc. are said to inhabit the Veil, which acts as a window into or mirror of our world.
They have a limited ability to reach through the Veil for the sake of communication, as the Veil overlaps the corporeal realm.
The Spirit World has been described in a variety of ways by different Spiritualists, such as Swedenborg and Blavatsky.
Tomekeeper's description of the Netherworld seems to overlap with these concepts of a Spirit World.
In fact, I think the Netherworld is a more accurate vision of the Spirit World than descriptions of heavens and hells.
This potentially overlaps with the Christian concept of Hades and the Vodoun concept of Guinea.
Pagan underworlds in general could potentially be distorted descriptions of the Spirit World from shamanic katabasis.
Spirits residing in the Veil are called ghosts, while spirits residing in the Spirit World are called shades.
The more culturally neutral terms for the Spirit World include "the land of the dead," "the Netherworld," and "the Underworld."
Tomekeeper makes a distinction between "hades" and "the realm of the dead," saying that hades is one place in the realm of the dead.
I disagree with this sentiment. There is only one place, but with many internal divisions, similar to a continent.
Tomekeeper does associate the Netherworld with the universal consciousness, which lines up with the perspective of Jungian Neoplatonism.
Traveling to the underworld is one of the oldest practices in necromancy, and many ancient rituals exist for this purpose.
I've used many of them, including Tomekeeper's, and they all lead to the same place, in my experience.
Tomekeeper's is one of the simplest and least demanding methods, so I recommend it over traditional ceremonies.
Tomekeeper and Wendell both agree that Death is best thought of as a metaphysical force.
Wendell seems to suggest that Death has some level of sentience, while Tomekeeper does not examine this possibility.
Death can be personified for the sake of being able to relate to him more personally.
These personifications are a double-edged sword, as they can easily obscure the underlying force.
We have to keep in mind that, while Death might take on familiar forms to interact with us, Death is greater than any of them.
Even if we can see representations of Death throughout various cultures, from Seker to Thanatos to Mot and beyond, these are only so useful.
There is a touch of eclectic paganism here, but the ancient pagans were in agreement that there is only one Death.
Where ancient pagans interacted, they tended to treat each other's personifications of Death as identical to their own.
This is a far cry from the hard polytheism of modern Western cultural relativists, who treat every name as a separate being.
I think the difference is because these ancient pagans believed in the literal, objective existence of Death as a supernatural being.
Tomekeeper and Wendell's works follow in this belief, although they incorporate a variety of New Age ideas when describing it.
Nonetheless, the underlying idea that Death is a force of nature that we can interact with is itself an ancient one.
The New Age influence involves speculation on what that means and how these interactions can take place.
Personally, I tend towards Spiritualism and goetia more than New Age energy work, relying on the Spirit Model more than the Energy Model.
Despite this, Wendell and Tomekeeper provide decent instructions for communication, katabasis, invocation, evocation, and so on.
They also accurately characterize attunement to Death and the way his presence feels.
For this reason, I do not mind the extra ideas tacked on from the New Age movement, even if I am slightly more traditional.