The Harm spell is the reverse of Heal and causes massive damage instead of healing.
To maximize the chances of success, the caster should have a good THAC0. It is therefore best used by a multi- or dual-classed caster. Multi-classed Fighter / Druids, Fighter / Clerics and Cleric / Rangers can achieve a 100% success rate by using the Critical Strike High-level class ability in combination with this spell.
This spell is the reverse of Heal. Instead of healing the creature touched, it causes damage. On a successful touch from the priest, the spell reduces the target to 1 Hit Point. The next attack that the priest makes will inflict this effect; however, the priest only has 2 rounds to make the attack before the spell fizzles. If the priest misses the target creature, the spell is wasted. There is no Saving Throw.