Radiation

Radiation is energy sometimes produced by materials and sometimes by physical interactions, such as the contact of matter with anti-matter.

Biological effects
Radiation is often harmful or fatal to most life and can cause mutations. Some organisms can withstand large amounts of radiation, such as the Foamasi, while others can actually absorb and regenerate with it, such as the Kastrians (DW: The Hand of Fear) or beings such as the Daleks on Skaro who's evolution led (at various points) to them becoming dependent on a constant supply of radiation. (DW: The Daleks)