Self: (physical mutation) A mutant with this ability can change the molecular structure of his body to increase his armor class or move more rapidly. To achieve a better armor class, the mutant's body shrinks and becomes more dense. Shrinking raises the armor class in direct proportion to the size change. A one-half size mutant has twice the normal armor class. A one-eighth size mutant is too dense to be punctured by any type of sword, spear, arrow, etc. However, becoming denser also decreases movement and reflex actions by the same amount, so that one-eighth size mutants are slowed to one-eighth normal speed.
To become less dense involves a size change the other way, and the mutant becomes larger. This lowers the armor class and strength, but allows faster movement. A twice normal size mutant is four armor classes lower than normal, but can move four times as fast as usual. A mutant may only expand to twice its normal size. There is no limit to the number of times a mutant may change its density and the change is instantaneous.
Others: (mental mutation) As above, but give it a range of 30 meters (almost 100 feet), and use it as an offensive or defensive power on other beings.