From Compendium of Worldly Lore
The holy scourge is a multitalented soldier in the endless war against evil, an arcane caster who instills within his magic the power to cleanse the world of wickedness and depravity. Although he lacks actual divine spellcasting power, he makes up for this shortfall by infusing his evocations with holy power and developing abilities that help him smite evil wherever it appears.
Almost any arcane spellcaster can become a holy scourge, but the class is most popular among sorcerers and warmages. Wizards, particularly those who specialize in evocation or conjuration, also find much to like in this prestige class.
Role: Spell Support
Characteristics: Scourges of evil that blend divine paladin traits with arcane casters.
Source: Complete Mage
Game Rule Information
The Holy Scourge has the following game statistics.
Abilities: Your casting stat is by far the most important and that may not be charisma or wisdom, so pick the appropriate mental stat. Dexterity is another important one so you can make your spell attack rolls against evil foes.
Alignment: Any Good
Hit Die: d6
Starting Gold: N/A
Class Skills
The Holy Scourge's class skills are Concentration (Con), Craft (Int), Knowledge (arcana) (Int), Knowledge (religion) (Int), Knowledge (the planes) (Int), Listen (Wis), Profession (Wis), Search (Int), Spellcraft (Int), and Spot (Wis)
Skill Points at 1st Level: (2 + Int modifier) × 4
Skill Points at Each Additional Level: 2 + Int modifier
Class Features
All of the following are class features of the Holy Scourge.
Weapon and Armor Proficiency: A Holy Scourge is proficient with whatever they were already proficient with prior to taking levels in this class.
Spellcasting: At each level beyond 1st, you gain new spells per day and an increase in caster level (and spells known, if applicable) as if you had also gained a level in a spellcasting class to which you belonged before adding the prestige class level. You do not, however, gain any other benefit a character of that class would have gained. If you had more than one spellcasting class before becoming a holy scourge, you must decide to which class to add each level for the purpose of determining spells per day, caster level, and spells known.
Code of Conduct: You must devote yourself to the destruction of evil, particularly those who use evil magic and innately evil creatures. You must not resort to evil methods to achieve these goals. You might briefly ignore a lesser evil for the sake of defeating a greater one, but otherwise you must make every reasonable effort to obliterate evil wherever you find it. Should you ever violate this code or step outside the boundaries of what is considered acceptable good-aligned behavior, you lose your holy scourge class features.
Dedicated Spellcaster Ex: You gain a +1 bonus to your caster level when casting good spells. You may not cast evil spells.
Righteous Evocation Su: Your evocation spells are infused with a small amount of good-aligned divine energy. Against evil creatures, your evocation spells deal an extra 1 point of damage per spell level. This extra damage applies to all creatures damaged by the spell. This extra damage consists of pure divine energy and is not subject to being reduced by resistance or immunity.
At 5th level, this extra damage increases to 2 points per spell level.
Arcane Smite Su: At 2nd level, you can smite evil once per day. This ability functions like the paladin class feature (PH 44), except that you can apply the effect only to an arcane spell that requires a melee or ranged attack roll (such as shocking grasp or scorching ray). In addition to the bonus on the spell's attack rolls and damage rolls, this adds the good descriptor to the spell.
At 4th level, you can use this class feature twice per day.
Devoted Arcanist Ex: Beginning at 3rd level, you can add your class level on caster level checks made to overcome the spell resistance of evil creatures with your arcane spells.