NETHER DEMON
Large Outsider (Evil)
Hit Dice: 20d8+140 (230 hp)
Initiative: +10 (+6 Dex, +4 Improved Initiative)
Speed: 30 ft.
AC: 35 (+6 Dex, +20 natural, -1 size)
Attacks: 2 claws +27 melee, bite +27 melee or by weapon +27/+22/+17/+12/+7
Damage: Claw 2d8+7, bite 1d10+7 and poison
Face/Reach: 10 ft. x 10 ft./15 ft.
Special Attacks: Spells, spell-like abilities, poison
Special Qualities: Damage reduction 30/+3, SR 30, demon qualities, regeneration 5, dimension travel
Abilities: Str 27 Dex 22, Con 24, Int 20, Wis 20, Cha 20
Saves: Fort +19, Ref +18, Will +17
Skills: Alchemy +10, Bluff +22, Concentration +25, Diplomacy +22, Gather Information +21, Hide +24, Intimidate +18, Knowledge (any two) +22, Listen +30, Move Silently +24, Scry +18, Search +23, Sense Motive +23, Spellcraft +25, Spot +30
Feats: Cleave, Great Cleave, Improved Initiative, Power Attack, Sunder
Climate/Terrain: Any land or underground
Organization: Solitary
Challenge Rating: 20
Treasure: Standard coins; double goods; standard items
Alignment: Always evil (usually lawful)
Advancement Range: 21-40 HD (Large)

Nether demons are the lords and rulers of the lesser undead and shadow realms. Though subject to the commands of Mephistopheles and the arch demons, each nether demon rules his own fiefdom inhabited by undead and demons. Because they are confined to the abysmal planes of the undead, nether demons despise all living creatures and covet them as slaves and objects of torture and humiliation. Terrible battles are often fought between the undead armies of one nether demons and the hosts of a rival nether demon, with the victor claiming the human (or demi-human) slaves of the losing side.
  Nether demons typically appear as tall, humanoid beings with clawed hands and feet, horns, and gaping mouths filled with long teeth. Most nether demons dress in regal and aristocratic attire encrusted with hellstones and other indigenous precious stones. Those nether demons who do not occupy the manors of their lord will often be found dwelling in their own castles and fortifications of infernal splendor and nightmarish visage.

Combat
In melee a nether demon will either rake with its claws and attempt to bite with its poisoned fangs. Some nether demons utilize weapons, and will most often be +3 or greater enchantment. 
  Spell-Like Abilities: At will–grant a limited wish (to nondemons only) as the spell cast by a 20th level sorcerer.
  Spells: Nether demons have the spell abilities of a 14th level sorcerer (DC 15 + spell level) and a 12th level cleric (DC 15 + spell level) with access to the domains of Death and Evil. 
  Dimension Travel (Sp): Nether demons can travel through the planes, as per the spell teleport without error, three times per day.
  Poison (Ex): Bite, Fortitude save (DC 27); initial damage 1d6 temporary Wisdom, secondary damage 2d6 temporary Wisdom. 
  Regeneration (Ex): Nether demons take normal damage from holy or blessed weapons of +3 enchantment or greater.
  Skills: Nether demons receive a +8 racial bonus to Listen and Spot checks.
  See Invisibility (Su): Nether demons continuously see invisibility as the spell cast by a 18th level sorcerer.