Gamma World: The Infinity Arc
The Mutant template can be added to any creature. Although mutant characters will gain extraordinary new abilities, they will also be subject to debilitating defects. The challenge rating or effective character level does not change, as the mutations and defects are designed to offset one another.
A mutant creature uses all the base creature’s statistics and special abilities except for those affected by mutations or defects.
Type: the creatures type changes to aberration, with the augmented subtype. Mutant aberrations do not automatically gain dark vision, they must instead pick or roll it as one of their mutation choices.
A mutant creature retains all the special qualities of the base creatures and gains the following:
Mutations: The mutant creature gains three mutations.
Defects: The mutant creature gains three defects.
Medicinal Incompatibility: The mutant is changed and thus does not benefit as easily from medicines designed for the base creature. For example, a mutated human might not take well to a drug designed for normal humans. A mutant must make a Fortitude save (DC 15) or suffer a random effect from the Medical Incompatibility table. Some mutations and feats (such as the Super Mutant feat) modify this save.
Adapted from Darwin’s World d20