That I am aware of, there is no official template
If there was, it'd be in The Book of Vile Darkness, or else one of the Fiend Folios. I'm sad to say that I don't believe there's a template that mirrors Saint in terms of flavor or mechanics.
But...
I can propose some adjustments for you. Try doing this to the Saint template:
Requirements: Swap the requirement for a Good alignment with a requirement for an Evil one. Swap the prerequisite Exalted feats for Vile feats, and require a great act of evil in the name of a dark god (personal suggestion: a sacrifice of good-aligned sapient beings equal to double the character's hit dice).
Numerical Bonuses: Swap all instances of "perfection" bonuses with "profane" bonuses in the same areas. You can probably leave the energy resistance alone.
Spell-Like Abilities: Check and see which of the SLAs are distinctly "good" and replace them with evil ones. Some of them can probably stay, however, so don't go too crazy here.
Everything else, if I remember correctly, can remain the same.
Prestige Classes
There's a couple of prestige classes that might be useful to you if the villain in question is a fiend (an evil-aligned outsider) - namely, Fiend of Blasphemy and Fiend of Corruption, both of which can be found in the various Fiend Folios. These prestige classes give powers that help the fiend to corrupt, debase, and destroy souls in the names of greater patrons (or just Evil Itsownself) and could be very useful in your endeavor.
This winds up getting away from the idea of the hulking thug rogue/barbarian; the solitary barbarian level is used to grant mobility and agility rather than strength and endurance. That said, this is a very vicious combat build with lots of dirty tricks, very capable of pouncing on opponents unawares and tearing into them in an unholy frenzy.
The Assassin
For a low-optimization, low-magic campaign, where you want to focus on stealth and skills but still be able to deal the hurt, you could do a lot worse than the core assassin prestige class. It gets a number of low-level spells, so it should not be a problem for low-magic, but if there’s little magic available, you definitely want what little you can get.
If alignment is an issue, consider the avenger: it replaces the Evil requirement with a Non-Chaotic requirement, which is often much more amenable to characters.
Spells
Spells are the reason you go this route. The assassin spell list is quite solid, for as small a list as it is, and it will likely fly well in a low-magic game.
This recommendation does assume that you have access, at the least, to Spell Compendium. The core assassin spell list leaves a lot to be desired. If you want to use the avenger, also make sure your DM is OK with adding the Spell Compendium assassin spells to the avenger list. That’s in line with the guidance in that book for non-core spellcasting classes on pg. 3, so it shouldn’t be a problem, but it’s a conversation you should have.
Psionics
The psionic assassin from Secrets of Sarlona also exists, and adds the very interesting option of using Expanded Knowledge for psionic minor creation, which is an excellent way to get poisons. That said, unless your DM allows other assassin spells to be converted into psionic counterparts, it’s not a great option. If you can, then you might as well?
Death Attack
Don’t focus too much on Death Attack; at best you can attempt it during a surprise round after spending three rounds studying your target out of combat. Attempting to hide and wait three rounds mid-combat is always a bad play.
Poison Use
Poison Use is meh; if you want to use poison, you want the Master of Poisons feat from Drow of the Underdark anyway. That said, Master of Poisons is a quite-solid feat, and Craft (poisonmaking) can get you poison at a huge discount (if you have a source of materials, ⅙ market price). Poisons provide a way to apply debilitating effects along with straight damage. See the Arsenic and Old Lace handbook for more details if you’re interested in going for poisons.
Again, if you are avoiding being Evil, you have to clarify something with the DM: poisons, according to Player’s Handbook and Dungeon Master’s Guide, are not evil, though usually illegal (and always dishonorable, which is why they are barred to paladins). Book of Exalted Deeds, however, says they are actually Evil – and then gives a definition/explanation of how and why they’re Evil that would include, for example, the natural poison of the couatl, that is, a notably Good creature. Book of Exalted Deeds is not a good book. Just make sure, if you don’t want to be Evil, that your DM agrees that Book of Exalted Deeds is stupid, and poisons aren’t any more inherently evil than swords.
Hide in Plain Sight
It’s a long time coming, but getting Hide in Plain Sight, along with taking the Darkstalker feat from Lords of Madness, will prevent a lot of the major ways to simply shut down your stealth. Highly recommended.
The Black Dog
This prestige class from Dragonmarked stacks with assassin levels for Death Attack DCs, and has a couple of excellent abilities aimed at poison. I’ve decided that poison is a good direction to take this, hence its appearance here.
The black dog requires the Mark of Hospitality feat, which in Eberron is limited to halflings. This is a matter of setting fluff, so if you aren’t playing in Eberron, the Mark of Hospitality might be available to half-orcs. On the other hand, I actually like halfling a great deal more than half-orc here. It does mean a shift from Strength to Dexterity which you may find undesirable, but half-orc is quite weak, and the halfling’s size is basically all to your benefit (average of −1 on damage rolls, but +1 attack, +4 to stealth, and +1 to AC). The existence of the strongheart halfling (Forgotten Realms Campaign Setting) really seals that deal.
Suggested Build
Strongheart Halfling Rogue 3/Barbarian 1/something 1/Black Dog 5/Assassin 10
At Rogue 2, the Penetrating Strike alternate class feature (Dungeonscape) is key, and at Barbarian 1, you really want the Lion Spiritual Totem alternate class feature (Complete Champion) to get Pounce instead of Fast Movement (you’re not a charger per se, but you do want to maintain mobility and full-attacks, and pounce is a really good way to do that).
I’d replace Rage with Ferocity, though I’d also consider Whirling Frenzy.
The something 1 I’m not sure about; barbarian 2 is OK but not great, rogue 4 is fairly mediocre...
Some options that should be no problem:
Fighter. You want Weapon Finesse at this point, so that’s a use for your bonus feat, and the Hit-and-Run Tactics alternate class feature from Drow of the Underdark trades some armor and shield proficiency you probably won’t use for +2 to initiative and Dex-to-damage vs. flat-footed foes, which is awesome.
Ranger. Simple: full BAB and 6+Int skills. Boring, but functional.
Anything that gives Sneak Attack +1d6 at first level. Again, boring, but functional.
Some options that probably aren’t allowed, but could be awesome:
Cleric. Best single-level dip in the game, bar none. Could be worth it even if you get none of its spells. Domain granted powers are awesome, and failing that you can trade them for Devotion feats (Complete Champion), many of which are excellent. Turn/Rebuke Undead is excellent for Divine feats, including the amazing Lolth’s Caress (Drow of the Underdark). While a halfling who worships Lolth is weird, with this build’s interest in poison it’s not a stretch to worship the goddess of spiders. Or if Lolth doesn’t exist in your setting, maybe you can just ignore that requirement.
Ardent or Psion. One level is sufficient to manifest psionic minor creation, which will get you a plant-based poison that lasts an hour. Not a bad deal at all.
Swordsage. Cloak of deception provides instant flat-footing for an enemy, once per encounter, while shadow jaunt provides great mobility. Wolf fang strike and sudden leap allow you to continue to dual-wield effectively even when you’re forced to move and cannot charge. If you later take Martial Stance, you can snag assassin’s stance for +2d6 Sneak Attack damage.
Anyway, you definitely want the Craven (Champions of Ruin), Darkstalker (Lords of Madness), Master of Poisons (Drow of the Underdark), and Weapon Finesse feats. Plus, black dog requires Mark of Hospitality (Eberron Campaign Setting).
The feats Extra Rage (Complete Warrior) and Wild Cohort could be very nice for you, if you can squeeze them in (maybe later, or if you take a Fighter level and have another feat to play with). Note that I don’t recommend Wild Cohort so you have a pet fighting alongside you: I recommend it so you have a reliable, cheap poison dispenser following you around. Unfortunately, both feats are kind of lackluster by the time they fit into the build I am proposing.
Anyway, your feats may look like this:
- Bonus racial feat: Weapon Finesse
- 1st-level feat: Master of Poisons
- 3rd-level feat: Mark of Hospitality
- 6th-level feat: Darkstalker
- 9th-level feat: Craven
- 12th-level feat: Extra Rage?
- 15th-level feat: Wild Cohort?
With this combination, your attacks hit hard, and you are hard to find. You have poisons that you can use selectively, and they are very dangerous. You have a smattering of spells that will make a huge difference in a low-magic world. Seems like a pretty solid approach to me.
Best Answer
Book of Exalted deeds gives the template of the risen martyr and the deathless creature:
Deathless is a new creature type, describing creatures that have died but returned to a kind of spiritual life. They are similar in many ways to both living creatures and undead. However, while undead represent a mockery of life and a violation of the natural order of life and death, the deathless merely stave off the inevitability of death for a short time in order to accomplish a righteous purpose. While undead draw their power from the Negative Energy plane, the deathless are strongly tied to the Positive Energy plane, the birthplace of all souls. In fact, the deathless are little more than disincarnate souls, sometimes wrapped in material flesh, often incorporeal and hardly more substantial than a soul in its purest state.
Features
• 12-sided Hit Dice.
• Base attack bonus equal to 1/2 of total Hit Dice (as wizard).
• Good Will saves.
• Skill points equal to (4 + Int modifier, minimum 1) per Hit Die, with quadruple skill points for the first Hit Die.
• No Constitution score.
• Darkvision out to 60 feet.
• Immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
• Immunity to poison, sleep effects, paralysis, stunning, disease, and death effects.
• Not subject to critical hits, nonlethal damage, or ability drain. Immune to damage to its physical ability scores (Strength, Dexterity, and Constitution) as well as fatigue and exhaustion effects.
Unlike undead, the deathless are subject to energy drain. Like living creatures, deathless are harmed by negative energy and healed by positive energy.
• Immunity to any effect that requires a Fortitude save, except for energy drain attacks, effects that also work on objects, and harmless effects.
• Cannot use the run action.
• Uses Charisma modifier for Concentration checks.
• Not at risk of death from massive damage, but when reduced to 0 hp or less, it is immediately destroyed.
• Not affected by raise dead and reincarnate spells or abilities. Resurrection and true resurrection can affect the deathless if they are willing. These spells turn deathless creatures back into the living creatures they were before becoming deathless.
• Evil clerics can turn or destroy deathless creatures as good clerics turn or destroy undead. Good clerics and paladins can rebuke, command, or bolster deathless creatures as evil clerics rebuke, command, or bolster undead.
• Deathless creatures gain the same benefits from consecrate and hallow as undead do from desecrate and unhallow, and they are hindered by desecrate and unhallow as undead are by consecrate and hallow. Hide from undead and undeath to death also work against deathless.
Detect undead and deathwatch also reveal deathless, and allow the caster to distinguish deathless creatures from undead. Evil casters can be stunned by overwhelming auras of deathless creatures as good casters can be stunned by overwhelming undead auras. Use the “undead” line in the detect evil spell description when deathless are in the area of a detect good spell.
Deathless are healed by disrupt undead and damaged by unholy water as undead are by holy water.
Deathless are not affected by disrupting weapons. Spells that have greater than normal effect against undead creatures—including chill touch, magic stone, searing light, sunbeam, sunburst, and wall of fire—do not have these enhanced effects against deathless creatures. Deathless take only 1d6 points of damage per two caster levels from searing light. Spells such as command undead, control undead, create undead, create greater undead, and halt undead do not affect or create deathless creatures.
• Proficient with its natural weapons and any weapons mentioned in its entries.
• Proficient in whatever type of armor (light, medium, or heavy) it is described as wearing, as well as all lighter types. Deathless not listed as wearing armor are not proficient with armor.
• Deathless do not breathe, eat, or sleep.
The Next Big one is the EIDOLON From ghostwalk
This class sub's levels and is perfect for a GM to transform a living party member or bring one back from the dead as a new class with a mission.
There is also the RISEN MARTYR from the Book of Exalted Deeds page 68:
This class is perfect for the GM to grant a single level in cause it's a prestige class and the first level is the hardest to achieve.