Immortal

Immortal Creatures will not die. Or, rather, they will just live for such a long time that you'll never see them die, unless you leave your game on forever and you can stay alive.

Some genetic mutations that can cause immortality are:
 * large amount of glycogen produced (see Highlander). This is a C1 only method!
 * decreasing the half-life of ageing/life
 * deleting the receptor to change life stages - the norn becomes 'stuck' in a lifestage
 * deleting the automatic death gene altogether

Note that the original C1 creatures did not have a gene that killed them automatically, and so were potentially immortal by default - they just died in other, more interesting ways.