Considering such creatures hell hounds at the top of their advancement range (8d8) comes close to defining the monster -- except for those extra heads. Just adding an extra bite attack to make a creature two-headed does not seem in keeping with the unique mythic nature of many multiheaded creatures. They should instead stand as paragons of their base species, possessing additional hit dice and all the improvements that go with them, in addition to multiple bites, gore attacks, and even breath weapons. To help Dungeon Masters create their own multiheaded creatures, I present the "multiheaded" template.
Multiheaded Creatures
Be they freaks of nature, the results of arcane experimentation, or simply a new race, some creatures have more heads than do common examples of their kind. Many multiheaded creatures are actually crossbreeds with some amount of hydra blood magically infused into them. All multiheaded creatures are more powerful and dangerous than similar creatures with fewer heads, and many become local legends.
It is not unusual for multiheaded creatures to be trained as guards and watchmen, as their increased number of eyes and noses equips them well for such tasks. However, a creature's heads don't always get along with each other, and this characteristic can make multiheaded guardians extremely unpredictable. In many cases, such creatures are simply forced into lairs nearby a stronghold, perhaps covering one of its secret entrances.
Creating a Multiheaded Creature
"Multiheaded" is a template that can be added to any corporeal creature with a discernable head. Animals with this template become beasts, but otherwise their type remains unchanged. If the base creature has different types of heads (such as a chimera), determine a specific type for each head. (Special Attacks are determined by head type in these cases.) Up to seven heads may be added to a base creature. Multiheaded creatures use all the base creature's statistics and special abilities except as noted below.
Hit Dice: Each additional head adds 2 HD to the base creature.
AC: Increase natural armor by +1 per additional head.
Attack: Creatures with bite or gore attacks gain one additional bite or gore attack per additional head.
Special Attacks: Base creatures who use weapons gain superior Two-Weapon Fighting. This feat allows them to use two weapons without any penalty to attack or damage. Base creatures with breath weapons or gaze attacks, or who can swallow whole, gain the ability to use that power with each head simultaneously. Special attacks (improved grab, poison, sonic attacks) related to a creature's head can be used with all heads at once.
Special Qualities: Multiheaded creatures have darkvision to 90 ft.
Saves: Same as base creature.
Abilities: Base creature's Constitution is increased by +2 per additional head.
Skills: Each additional head grants the creature a +2 racial bonus to Listen, Search and Spot checks. The creature also gains any additional skill points to which its additional Hit Dice would entitle it, according to its type.
Feats: Base creatures with a bite attack gain Weapon Focus (bite) as a bonus feat. The creature also gains any additional feat slots to which its additional Hit Dice would entitle it, according to its type.
Climate/Terrain: Same as base creature
Organization: Solitary
Challenge Rating:
1 additional head, +2
2-4 additional heads, +3
5-7 additional heads, +4
+1 additional per head-based special attack of base creature
Treasure: As base creature
Alignment: Always chaotic
Advancement: Same as base creature
Lernaean, Pyro- and Cryo- Creatures
Some multiheaded creatures have abilities similar to those possessed by the magic forms of hydras. Each type has a different ability.
Lernaean Creatures
These multiheaded creatures have bodies that are immune to attack (but see below). The only way to slay a Lernaean creature is to sever all its heads. However, each time a head is severed, two new heads spring from the stump in 1d4 rounds. A Lernaean creature may never have more than twice its original number of heads, and any heads it gains beyond that number wither and die within a day.
To prevent a severed head from growing back into two, at least 5 points of fire or acid damage must be dealt to the stump (AC 19) before the new heads appear.
Spells such as disintegrate, finger of death, and slay living kill a Lernaean creature outright if they succeed. If the spell deals damage on a successful save, that damage is directed against one of the creature's heads.
Pyro Creatures
These reddish creatures can breathe jets of fire 10 feet high, 10 feet wide and 20 feet long. All heads breath once every 1d4 rounds. Each jet deals 3d6 points of damage per head. A successful Reflex save halves the damage. The save DC is 10 + 1/2 the creature's number of heads + the creature's Con modifier. The creature also gains the fire subtype.
Fire Subtype (Ex): Fire immunity; double damage from cold except on a successful save.
Cryo Creatures
These purplish creatures can breath jets of frost 10 feet high, 10 feet wide and 20 feet long. All heads breath once every 1d4 rounds. Each jet deals 3d6 damage per head. A successful Reflex save halves the damage. The save DC is 10 + 1/2 the creature's number of heads + the creature's Con modifier. The creature also gains the cold subtype.
Cold Subtype (Ex): Cold immunity; double damage from fire except on a successful save.
Sample Multiheaded Creatures
The first sample uses an 8-HD hell hound to create a Cerberus knock-off. The second is a horrifying combination of hydra and gorgon using the gorgon as the base creature and adding seven heads.
Demonic Guardian Hound Large Outsider (Chaotic, Evil, Fire) Hit Dice: 12d8+60 (114 hp) Initiative: +4 Speed: 40 ft. AC: 18 (-1 size, +9 natural), touch 9, flat-footed 18 Attacks: 3 bites +17 melee Damage: Bite 2d6+5/19-20 Face/Reach: 5 ft. by 10 ft./5 ft. Special Attacks: Breath weapon (30-ft. cone of fire) Special Qualities: Darkvision 90 ft., fire subtype, outsider traits, scent Saves: Fort +13, Ref +8, Will +8 Abilities: Str 21, Dex 11, Con 21, Int 6, Wis 10, Chr 6 Skills: Hide +16, Listen +17, Move Silently +19, Search +5, Spot +17*, Wilderness Lore +7* Feats: Improved Critical (bite), Improved Initiative, Power Attack, Track, Weapon Focus (bite) Climate/Terrain: Any land or underground Organization: Solitary Challenge Rating: 9 Treasure: None Alignment: Always chaotic evilDemonic guardian hounds are three-headed advanced hell hounds.
Combat
Breath Weapon (Su): Each of demonic guardian hound's three heads may create a 30-foot cone of fire every 2d4 rounds. The attack deals 1d4+1 points of fire damage (Reflex DC 21 half). The fiery breath also ignites any flammable materials within the cone. All three heads may breathe at once, and the creature may use its breath while biting.
Fire Subtype (Ex): A demonic guardian hound has fire immunity, and it takes double damage from cold except on a successful save.
Outsider Traits: A demonic guardian hound has darkvision with a 90-foot range. It cannot be raised or resurrected (though a wish or miracle spell can restore life).
Scent (Ex): A demonic guardian hound can detect approaching enemies, sniff out hidden foes, and track by sense of smell.
Skills: A demonic guardian hound receives a +5 racial bonus on Hide and Move Silently checks. Because of its two extra heads, it also gains a +4 racial bonus on Listen, Search and Spot checks. *It gains a +8 racial bonus on Spot checks and Wilderness Lore checks when tracking by scent, due to its keen sense of smell.
Gorgahydra Large Magical Beast Hit Dice: 22d10+220 (341 hp) Initiative: +4 Speed: 30 ft. AC: 25 (-1 size, +16 natural), touch 9, flat-footed 25 Attacks: 8 gores +26 melee Damage: 1d8+5 Face/Reach: 5 ft. by 10 ft./5 ft. Special Attacks: Breath weapon (60-ft. cone of petrification gas), trample 1d8+7 Special Qualities: Darkvision 90 ft., low-light vision, scent Saves: Fort +23, Ref +13, Will +8 Abilities: Str 21, Dex 10, Con 31, Int 2, Wis 12, Cha 9 Skills: Listen +29, Search +10, Spot +29 Feats: Alertness, Cleave, Great Cleave, Improved Critical (gore), Improved Initiative, Power Attack Climate/Terrain: Temperate and warm land and underground Organization: Solitary Challenge Rating: 12 Treasure: None Alignment: Always chaotic neutral
Gorgahydras are bizarre hybrids of gorgons and hydras, likely created through arcane means. They have the body and metallic plates of a gorgon but have eight heads, some on long armored necks. Unlike gorgons, they dislike labyrinths, but still enjoy other rocky underground areas.
Combat
Breath Weapon (Su): Each of a gorgahydra's eight heads can create a 60-foot cone of petrifying gas every 1d4 rounds that permanently turns its victim to stone (Fortitude DC 31). Though the gorgahydra has eight heads, it cannot use its breath weapon more than five times each day, total.
Trample: A gorgahydra can trample Small or smaller creatures for 1d8+7 points of damage. Opponents who do not make attacks of opportunity against the gorgahydra can attempt a reflex save (DC 26) to halve the damage.
Low-Light Vision: The creature can see twice as far as a human in starlight, moonlight, torchlight, and similar low-light conditions.
Scent (Ex): The creature can detect approaching enemies, sniff out hidden foes, and track by sense of smell.
