How long can a preserved human body last before turning to dust?

Question

Some Context

The setting is a fantasy world with lots of magic where Liches exist.

A Lich is "born" through a series of complex, dangerous and horrific rituals that a mage casts upon himself over the course of years, decades even. In order to become a Lich, the mage has to do two things:

1. Cast several spells to protect his physical body from decay;
2. Transfer his "essence" into a vessel, which he will keep with him always.

The main objective of this ordeal is eternal life - or, at least, to greatly expand one's life expectancy.

While a human lives about 70 to 80 years in this setting, a Lich's lifespan is counted in hundreds of years.

A Lich's body will still age, but at a much slower rate. It will eventually decay and turn into a living skeleton, until the anti-decay spells can't stop him from turning into a pile of dust. As the decay advances, he continuously uses magic to keep himself together and "emulate" whatever he needs to (like his voice).

The Question

What I want is to determine a Lich's lifespan based on actual facts about the decay speed of a preserved human body through existing means, like embalming.

So... how long can a human body be preserved before turning to dust?

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Side Note

I've come across two pieces of information before writing this question:

1. I've seen a rough estimate that a human body will completely decay in about 8 years without any kind of preservation;
2. Some older questions pointed out that a correctly preserved body might stay preserved indefinitely.

I'm not interested in either of these options - the first is too short and the second is way too long. The ideal answer is not the perfect preservation technique, but one that will keep it alright for a considerable amount of time. I will, then, use this number as an estimate to state how long my Liches' bodies last.

Answer 1

I cannot give you a definite answer, but there are several aspects to consider.

A perfectly embalmed Egyptian mummy in it's tomb can exist indefinitely because it's not moved around and lacks the moisture to decompose. As soon as it's handled by people, it takes damage.

Liches move around but don't heal. Every tiny scratch and cut will eventually accumulate until there's nothing but dust left. Even the subtle movement of robes over skin will eventually wear the skin and tendons away if they cannot regenerate.

Compare the different components of a body to preserved or processed materials:

• The outer skin will wear away at the same speed as leather. Wearing clothes, handling objects and even sitting down wears it away. Within a few decades, there won't be much left of it.
• Muscles and tendons are more robust, but prone to drying out and breaking or flaking away. I don't know how fast bare muscles wear away, but once they're gone, there's nothing left connecting tendons and bones. With proper care (like rubbing them with oil to keep them smooth) I'd estimate they add a hundred years or more to the unlife of a Lich after the skin is gone. Without proper care, they're gone in no more than a decade.
• Bones are comparable to ivory but the movement of joints will eventually wear them away in a severe case of attrition. Since Liches are prone to avoiding any physical labor, they may last a few hundred years, maybe up to a thousand.

BUT: Some limbs may simply fall of if the tendons connecting them to the body decay first. The feet are probably the first to fall off because they have to carry the complete weight of the body and move (literally) with every step. If the tongue or lips decay, the Lich has serious problems speaking and pronouncing his spells correctly.

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Interesting addition by Ralph Bolton:

Since we're magical, could the Lich use some sort of 'astral projection' to appear to be somewhere whilst his/her body remains at home? Even a Lich laying on a bed would endure some form of decay, but it would be considerably slower than walking about and generally being active. I guess some interactions with the outside world could escalate, demanding actual physical presence versus 'projected presence' too. Such requirements would have to be carefully rationed to ensure maximum longevity though.

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And don't forget the army of skeletal minions with fly swatters keeping little corpse-eating insects at bay.

Answer 2

Mummification goes a long way into preserving a corpse. According to Wikipedia, some mummies are over seven thousand years old.

But let's face it. You want to go Lich because the human body sucks. Why not take it up a notch?

Mummies can only survive for millenia at chill temperatures. I believe that inside liquid nitro they could last for millions of years, maybe billions. So get your lich assets into one of these:

It's where gullible rich people store their remains in hopes of living forever. Add some tank treads and big robot arms and not only will you really live forever, you will also be a Daft Punk song made true. You can also add guns. And internet. The liquid nitrogen environment also helps in overclocking any electronics you may wish to bring along.

Answer 3

There are a variety of preservation techniques with different results. Obviously you want to avoid ones where the body is not free to move around. Extensive wrapping, immersion, etc won't work unless the techniques are temporary.

Desiccation. Drying the body in a warm arid place will preserve it for a long time. Moving the body around after that, and exposing it to humidity, will slowly weaken it, which may give you your sweet spot of a few hundred years.

Coastal hunter-gatherers in the Atacama Desert of northern Chile and southern Peru, known as the Chinchorro culture, were among the first to perform artificial mummifications. Under a scenario of increasing population size and extreme aridity (with little or no decomposition of corpses), dead individuals may have become a significant part of the landscape, creating the conditions for the manipulation of the dead that led to the emergence of complex mortuary practices as early as 5000–6000 BC. (ref)

Salt can help preserve while keeping the body from becoming too dried out (which makes it brittle).

Prior to the introduction of carbolic acid, or phenol, and later of formaldehyde, the main preserving agents used in anatomies were alcoholic solutions of arsenic and/or alumina salts in different concentrations....Coleman & Kogan (1998) used almost the same chemicals (they replaced alcohol by isopropyl alcohol), but added a vast amount of sodium chloride. They argued that the high salt content retained in the tissues prevented any further significant desiccation. Salts have also been used...and 1% of anhydrous calcium chloride...and 5% of potassium nitrate. (ref)

There are multiple preserving agents and different combinations of them preserve tissue in different ways. You will want something that allows the body to move and look sort-of normal. Given that you will be using the body and exposing it to bumps and motion and stretching, plus air and humidity and maybe even rain, it will not last as long as it would in a tomb.

Answer 4

Have you looked into warhammer 40k's tech-priests? Although starting with a human base they can replace and augment their failing bodies with more and more technological bits (or in your case, magical) untill they can barely register as human anymore.

Also a Ship-of-theseus problem: which bit of the body is the "soul" anchored to? just the largest part? Because what happens to the bits that fall off? You could end up with a Ebbonwood-and-silver manequin with a bare skull bolted on top.

Taking the comments below into consideration: it would vary with the degree of crazy in the particular lich. Some might tyr to live lives like they still had a normal body (and as such would wear away quite quickly amid the buzzing of meat-flies) and others might try various forms of mummification, magical preservation or the replacement of the parts that they leave behind. You could even have a lich who tries to posess 'fresh' bodies, althought that would take so much magical focus that they woudn't be nearly as powerfull anymore.