Half-Fiend/Half-Medusa* (CR 9)

Medium Outsider (Evil and Lawful)
Alignment: Always lawful evil
Initiative: +4 (Dex); Senses: Listen +6 and Spot +10


AC: 18 (+4 Dex, +4 natural), touch 14, flat-footed 14
Hit Dice: 6d8+12 (39 hp)
Fort +4, Ref +9, Will +6
Speed: 30 ft., fly 30 ft. (average)
Space: 5 ft./5 ft.
Base Attack +6; Grapple +8
Attack: Claw +10 melee (or dagger +8 melee), bite +3 melee, snakes +5 melee; or shortbow +10 ranged
Full Attack: 2 claws +10 melee (or dagger +8/+3 melee), bite +3 melee, snakes +5 melee; or shortbow +10/+5 ranged
Damage: Claw 1d4+2; dagger 1d4+2; bite 1d6+1; snakes 1d4+1 and poison; shortbow 1d6
Special Attacks/Actions: Petrifying gaze, poison, spell-like abilities
Abilities: Str 14, Dex 19, Con 14, Int 16, Wis 13, Cha 17
Special Qualities: Poison immunity; acid, cold, electricity, and fire resistance 20
Feats: Point Blank Shot; Precise Shot; Weapon Finesse (snakes)
Skills: Bluff +12, Diplomacy +8, Disguise +12, Knowledge (any one) +7, Listen +6, Move Silently +13, Sense Motive +6, and Spot +10
Advancement: 7-12 HD (Medium-size)
Climate/Terrain: Any land and underground
Organization: Solitary or covey (2-4)
Treasure: Double standard

Source: Monster Manual (3E)

Unlike medusas, half-fiend/half-medusas are never mistaken for humans at any distance (the large bat wings give them away). Other medusas do not automatically reject these crossbreeds - in fact, they usually accept them as rulers.

Combat

More than their non-fiend siblings, half-fiend/half-medusas attack with aggressiveness and battle lust. They enjoy torturing their enemies.

Spell-Like Abilities: 3/day - darkness; 1/day - desecrate and unholy blight. These abilities are as the spells cast by a 6th-level cleric.

Petrifying Gaze (Su): Turn to stone permanently, 30 feet, Fortitude save (DC 15).

Poison (Ex): Snakes, Fortitude save (DC 15); initial damage 1d6 temporary Strength, secondary damage 2d6 temporary Strength.

Evil Subtype

A subtype usually applied only to outsiders native to the evil-aligned Outer Planes. Evil outsiders are also called fiends. Most creatures that have this subtype also have evil alignments; however, if their alignments change, they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has an evil alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the evil subtype overcomes damage reduction as if its natural weapons and any weapons it wields were evil-aligned (see Damage Reduction).

Lawful Subtype

A subtype usually applied only to outsiders native to the lawful-aligned Outer Planes. Most creatures that have this subtype also have lawful alignments; however, if their alignments change, they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has a lawful alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the lawful subtype overcomes damage reduction as if its natural weapons and any weapons it wields were lawful-aligned (see Damage Reduction).

This is a sample creature derived from a Template.