You draw an indelible mark on the subject and state some behavior on the part of the subject that will activate the mark. When activated, the mark curses the subject. Typically, you designate some sort of criminal behavior that activates the mark, but you can pick any act you please.
Since this spell takes 10 minutes to cast and involves writing on the target, you can cast it only on a creature that is willing or restrained.
A mark of evil is invisible most of the time, so it is possible for the subject not to realize he has been so marked - if he was unconscious while being marked for example. The mark of evil is a mar on the subject's immortal soul that has two effects.
First, anyone so marked who is in the area of effect of a detect evil spell is detected clearly in the first round of the spell. In fact, the person casting the detect evil sees the mark hovering over the subject's head, which clearly indicates that he is evil. The mark carries with it whatever clear information about the subject's crimes you wish to convey to others in a simple form. For instance, it is common for necromancers to be given the mark of evil in the form of a runic "N". Later, if they are caught in a detect evil, the caster of that spell will immediately see the subject has been caught and marked as a necromancer in the past.
Second, should the marked subject die, he may not be brought back from the dead for at least one year and a day. This is because the mark is clear on his soul in the land of the dead. its presence weighs more heavily on him when he is judged than most transgressions recorded in his black ledger. When Tiwas judges someone with the mark of evil, the subject is kept in chains in the land of the dead for a year and a day, rendering it impossible to revive such a person with a raise dead spell - or any other spell - within that time. The mark is an indication to Tiwas that this creature has been deemed a deeply evil criminal by his worshippers. In lands where execution is a punishment for various evil crimes, the worst criminal are often given a mark of evil and then executed.
It is possible to be marked with both a mark of justice and a mark of evil. These marks must be removed individually.
A mark of evil cannot be dispelled, but it can be removed with a break enchantment, limited wish, miracle, remove curse, or wish spell. Remove curse works only if its caster level is equal to or higher than your mark of evil caster level. These restrictions apply regardless of whether the mark has activated. A mark of evil can also, in some circumstances, be removed with an atonement spell.