A lich is an undead creature, typically a spell caster of some type that has who has used its magical powers to unnaturally extend its life. But not all lichs are the same.
How old are they? What species are they? Why did they become a lich in the first place?
All these aspects and more are covered in this volume of the CDG. The CDG (Creature Description Generator) range is designed with a fantasy setting in mind, but can easily be used for sci-fi or modern/horror settings.
The aspects covered:
Age - What is the apparent age of the Lich? At what age where they transformed into a member of the undead?
Condition - Lichs can range from being almost living, to virtual skeletons and this aspect gives you a few suggestions as to what that condition may be.
Death - When they became a lich, they had to die or have something similar to death applied to them. How did this occur
Lair - Where does the lich call home? Is it a grand castle or do they dwell in a cave behind a waterfall?
Personality - What sort of personality does the lich have? Are they, for a lich, kind or cruel and uncaring?
Phylactery - The phylactery is one of the hallmarks of a lich as it can house their soul or power source. What is the nature of this vessel?
Reason - Why did they become a lich in the first place? Was it through choice or was this state of undeath forced upon them from an angry god?
Servants & Minions - Does the lich any servants to add it or minion to boss around and do its bidding?
Species - The majority of lichs seem to be human males for some reason, but other species have found the path to lichdom as well, sometimes through choice. What species does the lich belong to?
Quirks & Features - Not all lichs are the same. Many have unique quirks and features that help stand out and be more memorable. Roll once on this table to find out what that can be. It might be something about the lichs phylactery, the fact they are female pretending to be male or something else entirely.