Looking at the options in the DMG both the Necromancer and Oath Breaker fit perfectly in to Oriental Adventures.  However, that only covers Tainted and fallen Sohei (Paladin) and Shukenja (Cleric).  Here is a non-caster option and the Maho-Tsukai works for arcane casters.

When using the villainous options from the Dungeon Master’s guide add the Maho spells to both the cleric and paladin.  They otherwise remain unchanged.


The Madmen of the Shadowlands

When a character’s Taint exceeds the capacity of his body and soul to contain it, he is possessed by the evil power of the Shadowlands and transformed into a creature of Taint. Such characters feel an irresistible urge to travel into the Shadowlands, often walking until their feet bleed, slaughtering anyone in their way.

The lucky ones are killed by Crab patrols or marauding Shadowlands creatures. The unlucky ones find their way to the Festering Pit of Fu Leng and are transformed into living servants of evil.

Most maho-bujin were Crab fighters, samurai, or rangers before their Taint overcame them.  NPC maho-bujin are found throughout the Shadowlands, often serving as commanders for small groups of Shadowlands creatures.

Beginning when you choose this archetype at 3rd level, you gain the Shadowlands type (which means you are affected by Shadowlands and Taint specific spells).  You are also vulnerable to jade weapons.

By definition, a maho-bujin is overwhelmed with Taint, but this Taint is not immediately obvious to onlookers.  After you become a maho-bujin, your Taint manifests in mental effects — insanity, rage, nightmares — and internal physical effects.  If a maho-bujin is split open, the internal corruption is obvious:  Your body is full of bloody pus and strange growths, even internal limbs.  Barring this condition, it is impossible to detect a maho-bujin based on appearance.

Additionally,  you no longer apply your Taint score as a penalty to your Constitution, but still applies half of your Taint score as a penalty to your Wisdom.

Starting at 7th level, you can use your bonus action to make an unarmed attack.  You are considered proficient in unarmed weapons if not already and your base damage is 1d6.  If you are a monk you may instead make two attacks using your bonus action.

At 10th level, who you strike the killing blow to dispatch any creature, you 5 + your Constitution modifier as temporary hit points and +2 to Strength (to a maximum of 30).  If you are a spellcaster who uses blood-magic (like a Tainted ranger), your effective spell DC increases by +1.  This effect lasts for 1 minutes per HD of the slain creature.

Starting at 15th level, you can add half your Taint score to your weapon attack rolls.

At 18th level, you are a champion of chaos and become an unstoppable killing machine.  You gain resistance to bludgeoning, piercing and slashing weapons that are not magical or jade.