Dark magic

Dark magic refers to any spells that diminish the physical, mental, or spiritual well-being of the user when cast. While nearly any spell of significant power can cause some damage if improperly cast, only those that cannot be cast by a typical, trained user without harm are classified as "dark".

Dark magic causes damage by improper or careless manipulation of essence. Typical side effects of dark magic include, sorted in approximate order of severity:
 * Physical: blackened tissue on the hands, loss of eye color, loss of strength, stamina, and/or fortitude, partial or total paralysis of limbs
 * Mental: Nightmares, hallucinations, schizophrenia

The spiritual effects are harder to pin down. The effects are not known to be reversible, and extensive use of dark magic inevitably leads to death.