There is a picture of the front page of the article somewhere in this thread.
Ah, I found it in Dragon Magazine #106. Briefly, they seem to be a Paladin/Rogue mix with a focus on lawful evil. They are a partial caster and can use Thief skills and basically half level, and they assassinate.
THE ILLRIGGER
Lawful Evil, with oaths to not be chaotic. Often devil worshippers.
Heavy armor, Morning star weapons (primarily)
Wisdom and intelligence are the prime requisites
The special abilities of an illrigger are:
1. A continual emanation of a protection from good spell.
2. Immunity to all forms of disease.
3. Detection of good at 5' per level.
4. Saving throw bonuses against chaotic magic at +1 for each three levels
5. Spell use at 5th level and above.
6. The use of certain thief functions at a level of ability equal to half the level of the illrigger
7. The ability to attack on the assassins table for assassinations after surprising an opponent.