The Paradigm Worlds are always evolving - literally! EVERY troop in the game, including the Player, gathers mutagen in their body over time. Even unique characters can mutate, if the option for this is turned on.

Once you gain a certain mutagen level, the exact amount of which you can find in the 'Reports' menu, you will 'reincarnate.' Reincarnation changes your character in significant ways.
During this transformation, troop characteristics are changed in positive and/or negative ways depending on your Luck and Mutation skills.

When someone undergoes mutation, there is a random chance to lose or gain points to all attributes. Each two points of the Mutation skill raise the random value by 1, with a Mutation skill of 10 being guaranteed to give a character NO negative status changes during mutation.
The effectiveness of some bio-tech weaponry is also based on your Mutation skill.

At the end of each mutation cycle, you can choose to reincarnate as a different race for no cost, or spend either +75 Doomsday Ticks or 2 Mutation Skill points to stay as your current race.

With every cycle of reincarnation, your chance of becoming a skeleton in the next cycle increases.
Skeletons are the end of everyone's journey, and are not capable of reincarnating any further.