Is there a class, feat, or race that would allow me to make a character that can heal himself by consuming his enemies?
I already know undead and the like can heal through energy drain and negative levels, but I'm referring specifically to physical consumption, not any type of energy-based stuff. And I'm aware of spells like goodberry, but that's not my character eating his enemies.
TL; DR Although not a perfect fit, consider the feat Voracious mentioned below.
"Medium characters need at least… about a pound of decent food per day to avoid starvation," says the Dungeon Master's Guide on Starvation and Thirst. Then a little later it says
A character can go without food for 3 days, in growing discomfort. After this time, the character must make a Constitution check each day (DC 10, +1 for each previous check) or take 1d6 points of nonlethal damage.
Characters who have taken nonlethal damage from lack of food… are fatigued…. Nonlethal damage from… starvation cannot be recovered until the character gets food…, as needed—not even magic that restores hit points… heals this damage. (304)
Thus, really, any creature that eats food to survive can potentially benefit from eating its foes in that a desire to eat one's foes significantly expands a creature's notion of decent food. The aberrant feat Scavenging Gullet facilitates this notion, allowing a creature to "gain nourishment from eating any organic material, despite its freshness or source" (Lords of Madness 181). Have fun with that.
If this is the route being traveled, even more fun might be just playing a kobold (Monster Manual 161—2). Races of the Dragon includes further details about kobolds, but the one we're interested is on Physiology that says, "Kobolds who are desperate for food, especially when traveling through cold regions, can eat almost anything. They can metabolize many forms of organic matter, including bark, bones, dirt, leather, and shells" (40) without needing a feat to do so. Presumably, a kobold can even gain nourishment from eating an earth elemental.
Weaponizing eating one's foes is a lot tricker. The headliner for that strategy is the prestige class illithid savant (Savage Species 77–9). Like the prestige class beholder mage (LoM 42–4), the prestige class illithid savant was an attempt to make a prestige class exclusively for a specific monster, but, also like the beholder mage, folks bring up the prestige class illithid savant as an optimization tool because it's frighteningly powerful—and, by almost all accounts, extremely broken. The class's abilities allow it to eat the brains of its foes so as to acquire forevermore those foes' feats, skills, and special abilities. Seriously, chances are—even if the requirements can be met by a PC (probably through the PC changing her races by being the subject of the 8th-level Sor/Wiz spell polymorph any object [trans] (Player's Handbook 263) or something)—that the DM won't let a player's PC enter the class unless the party is heavily optimized.
To be clear, though, while consuming a brain does give a savant a lot, doing so doesn't heal the savant. In fact, I'm pretty sure nothing does exactly what it sounds like the question wants. That is, there's no special ability that I'm aware of that's like When you deal to a living creature at least 1 point of lethal damage with your bite, you heal 1 point of damage or anything. However, below are some other options to consider.
Finally, to my knowledge, besides the prestige class illithid savant, the only billed-as-a-cannibal class that I'm aware of in official material is the prestige class flesheater (Dragon #300 68–9), but despite its name, despite a class feature called tooth and claw, and despite a requirement that entrants "must have all of their teeth sharpened to points" (69), none of the prestige class's class features encourage or even facilitate consuming foes.
As indicated it might be acceptable, there is a base class in Pathfinder, the Witch class. The relevant portion of the description is bolded:
Some gain power through study, some through devotion, others through blood, but the witch gains power from her communion with the unknown. Generally feared and misunderstood, the witch draws her magic from a pact made with an otherworldly power. Communing with that source, using her familiar as a conduit, the witch gains not only a host of spells, but a number of strange abilities known as hexes. As a witch grows in power, she might learn about the source of her magic, but some remain blissfully unaware. Some are even afraid of that source, fearful of what it might be or where its true purposes lie.
At 10th level, one of the major hexes that becomes available is the hex Cook People. The text of the hex is as follows:
Effect: Using this hex creates one meal or serving of food of the witch’s choice, typically a delicious stew or a dough suitable for cookies, pastries, or other desserts. Cooking the victim takes 1 hour. Eating the food provides one of the following benefits for 1 hour: age resistance, bear’s endurance, bull’s strength, cat’s grace, eagle’s splendor, fox’s cunning, neutralize poison (instantaneous), owl’s wisdom, remove disease (instantaneous). Alternatively, the witch can shape the dough into a Small, human-like creature, animating it as a homunculus for 1 hour. The witch must have the cauldron hex to select this hex. Using this hex or knowingly eating its food is an evil act.
As it already has curative properties, you could simply add healing as a benefit, or trade it for one of the current properties. If you want it earlier, simply make it a healing effect only, and add the other effects as you level up.
In fact, you can’t not know how to do this as a Cleric.
This is actually completely possible. The 3rd level Cleric spell rejuvenative corpse (SpC 172) targets a humanoid that died in the past week and charges their corpse with negative energy. On eating a full meal from that corpse, an undead creature gains fast healing 1 for 5 minutes (i.e. heals 50 hp).
So, the only tricky part is being undead. It’s likely that the feat tomb-tainted soul (Libra’s Mortis) will make this just work, but the wording of rejuvenative corpse is juuust ambiguous enough that it might not. Next best option is probably the Necropolitan template (also Libris Morris), which makes you actually undead.
Other than that, just stack levels of Cleric until you can cast the spell, stab fools, cast away, and chow down.
tl;dr—Book of Vile Darkness’s absorb strength allows a caster to eat a corpse and gain Constitution (and Strength); increasing Constitution grants more hp and max hp, so it’s kind of like healing, albeit only temporarily. Nothing else I’ve found really fits the bill.
Bizarrely, there are not a lot of options along these lines, not even among monsters oddly enough. I suspect there was a certain amount of “well if the PCs are dead it doesn’t really matter what the monsters do” going on there, but it does limit us somewhat. The best answer so far, by my estimation—HeyICanChan’s suggestion of the Voracious feat—is still only licensed work, not Wizards of the Coast material.
I can’t offer any better, but since I spent a lot of time looking through material for even these meager suggestions, it seemed silly not to post them:
Book of Vile Darkness has “corrupt spells,” which any spellcaster can prepare (yes, prepare—you can’t get them if you don’t prepare your spells, though the Arcane Preparation feat can help). They all deal ability score damage to the caster after they have completed, and they are all tagged with the evil descriptor. Since none of them heal you, and then they all wind up dealing ability damage to you, they really don’t apply, but several of them do involve eating foes.
Book of Vile Darkness also has the lifedrinker prestige class for vampires, as well as the soul eater prestige class, which allow healing and more from drinking blood or eating souls, respectively, but both must be inflicted on the living.
The first thing I thought of was to look into monsters that can do this, and then use shapechanging magic to turn into one. Since that ability is likely a supernatural one, you would need some ability to get supernatural features while polymorphed—either use powerful magic like shapechange, or take a feat like Assume Supernatural Ability from Savage Species or Metamorphic Transfer from Expanded Psionics Handbook (or the SRD since the feat is open-game content). For class, druid, wizard, and psion are probably the most likely candidates here, though monk or ranger could work through variants that get wild shape (Dragon vol. #324 and Unearthed Arcana/SRD, respectively). The master of many forms prestige class from Complete Adventurer will likely be important for opening up other creature types, since an ability like this is most likely found among things like aberrations and outsiders. Anyway, normally polymorphing, particularly polymorphs that include supernatural abilities, are some of the quickest ways to break the game, but limiting yourself to one particular form that has the feature you want does help a lot with reigning it back in, particularly since you aren’t going for an especially-problematic form.
Unfortunately, I cannot actually find any candidates here: the barghest kind of does it (gaining HD causes you to gain hp, after all), and the dusk giant from Heroes of Horror has a similar feature, but while gaining HD will increase your hp, it’s not really the same thing. An intellect devourer can eat the brain of a corpse (or soon-to-be-corpse) to take over that body; again, no healing. Tsochari from Lords of Madness can also pull that trick, and don’t even have to kill the target if they don’t want to—and they get to steal the target’s spell slots in the process. Still no healing.
The illithid savant prestige class from Lords of Madness can do even better if you turn into an illithid—eating brains allows the savant to steal all kinds of abilities and knowledge—but it doesn’t grant actual healing as requested. It’s also one of the most broken classes in the game, so I recommend against it.
Finally, there is swallow whole—a lot of monsters do have that. Swallow whole is a combat maneuver, though, and while it’s pretty effective at killing things, it doesn’t directly heal you. It also doesn’t let you do anything special with creatures you have already killed. But if you’re interested in it, in addition to polymorph effects to turn into something that can do it, there is also the 8th-level hunger domain spell bite of the king, found in Libris Mortis and Spell Compendium, which allows you to swallow creatures whole without having to change form.
Actually, I take back what I said about aberrations and outsiders being the most likely sources of such abilities: the undead are the ones most likely to have such a feature, but it’s likely to be obligatory, unlikely to be playable, and turning into an undead creature temporarily can be difficult. Of core spells, only shapechange can do it, and that’s a 9th-level spell. It’s hard to design a character around something you won’t have until 17th level, at best.
Libris Mortis does have a few playable undead “monster classes”—ghoul, mohrg, mummy, vampire spawn, wight, and necropolitan—but only the vampire spawn has anything close, from its blood drain ability. Again, like death knell, that only works on living targets, rather than already-dead ones (though it does not require they be dying), and grants temporary hit points, not true healing. And really, while playing a vampire spawn, or vampire, is legal under the rules, as a practical matter they are saddled with so many drawbacks in the name of balance that they actually become basically unplayable. The necropolitan is playable—it’s LA +0—but it doesn’t get any particular features aside from the undead type, nothing relevant here.
Incredibly, even ignoring the difficulty of actually managing to play some random undead, even looking at the ones I don’t think could be playable, I still cannot find any undead creatures that actually heal from eating corpses. I’m kind of flabbergasted by it, to be honest.
