The lich is by far one of the most powerful undead out in the world. The magic alone necessary to make one denotes how powerful the person was in life. several rituals are known for the process, all typically requiring a significant amount of magic to perform and often human sacrifice. the lich's soul is then kept in a vessel, typically a ring, or something easily hidden acting as a phylactery As long as it exists, the lich is functionally immortal.
However time does ware on the lich's body. over time bones do become more brittle, however its powerful magical essence will stop it from ever truly falling apart. Many embrace this change, seeing it as transcending into demi-lichdom, with powers rivalling a demi-god with knowledge of thousands of years. Others fear this, and go to lengths to see it stopped, even going as far as bronzing their bones, giving their body more durability and a form that will never truly rot away.
All liches are skeletal. during the ritual, their blood becomes a slight acid, making them feel untold pain, and burning away all flesh from their bones. Though there is a ritual that does not do this, the flesh still rots away in time, even with proper embalming, they will never pass as human again. However, most have powerful enough magic that this no longer matters, they can control thralls to acquire whatever they might need, or even have willing servants going out into the world for them.
Event he weakest of the liches rival the most powerful archmages human have to rival. if a lich so despires, much of the world could lay in ruin at their feet. Luckily liches are typically short sighted, and as tiem goes on earthly desires die entirely and they begin to gleam a bigger picture, that largely leaves them just to study their magic, and explore unearthly places.
Luckily, despite their power, liches aren't impossible to deal with. like most mages, they require specif movements to cast spells, their bones grow brital with time, so with proper distractions and close combat, they can be rendered generally ineffectual. however, they are able to channel their power into their touch, causing rot similar to that of a mummy, so if a hunter leaves and opening, it might be their last. Luckily this seems to be rather taxing so all but the very desperate, or very powerful tend to avoid using this. As well, there are a number of rituals available to track the essence from the defeated lich's body to its phylactery, which then properly dealt with destroys the lich forever.
It is commonly beleived that destroying the phylactery before defeating th elich will weaken it, this is not true, and sometimes the reserve can be true. Though killing it then will kill it forever, since part of it is left in the phylactery, you effectively just made th elich whole for the time being, though most tend to keep just the basic power in its phylactery, some leave a lot of pwoer there, causing you to just make a deadly foe more deadly.
It is worth stating that when the MRE has gone up against powerful liches in the past, there has often been pledged support from outide factions. Typically the MRI like to assist in hopes of learning more secrets of magic, as well to steal tomes or at least stake a claim to them so that the MRE is forced to share whatever secrets may lie with in. However, there has been times where Witches of the white have sent a small ditactment to assist, requesting no payment, and as well choirs of angels have appeared to assist in the final push in more then one lich assault. The Order of the black lotus' suggestion 'just attack its hand and library' have not been helpful however.
Most intereswting of all however was when a small band of dwarves appeared, and in clear english announced that they were going to help destroy this lich once and for all. It is beleived that the lich had been at war with these dwarfs, but all the same this was a one of a kind event. the dwarf ritualist proving to be almost a match for the lich its self. However after its defeat the dwarfs were nto to kind at helping the contact team leave its liar, claimign it as part of their dominoin, and it wa sonly by their good graces the contact team was not killed on sight.
In closing, Liches are powerful foes, but with proper planning, and ability, they are not much more difficult to deal with then a living wizard, however, they are never to be under estimated, as they are wily as they are old, and their liars and minds are laden with traps.