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:
- Cast several spells to protect his physical body from decay;
- 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).
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?
I've come across two pieces of information before writing this question:
- I've seen a rough estimate that a human body will completely decay in about 8 years without any kind of preservation;
- 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.