[Commissioned by @crazytrain48. Another Arduin Grimoire creature, another syncretism of the ideas from the original and the Arduin Legacy versions. The flaming blade appears to have been an embellishment of Brad Schenk, as the original version doesn’t include any reference to it in the text.]
Chaeronyx
CR 10 CE Monstrous Humanoid
This creature is humanoid from the waist up, and equine from the waist down. Its skin is rocky, blue-gray, and covered in stony carbuncles. A nest of vipers grows from its head, and its eyes glow a sinister green.
The chaeronyx are creatures halfway between a centaur and a medusa, more cruel and warlike than either. They live in the deepest, darkest forests, where they make frequent raids against other peoples. A chaeronyx is a carnivore with a taste for sentient meat. They rarely cooperate with each other besides small family units, and the foals remain with their parents until well into adulthood.
In combat, a chaeronyx trusts to its stony hide and petrifying gaze to protect it from most attackers. Their hate is channeled into the weapons they wield, manifesting as black fire that affects creatures in a similar fashion to a chill touch spell. If hunting for food, they will typically keep their distance and wear enemies down with arrows dosed with the poison from their snake-like hair.
Chaeronyx sometimes advance by character level. Those with a taste for religion favor the worship of demon lords or other especially wicked entities—lesser demons often view chaeronyx with something akin to jealousy. Chaeronyx antipaladins are especially feared, as their plots are typically wide ranging and more ambitious than the violent hedonism expressed by the typical chaeronyx.
Chaeronyx      CR 10
XP 9,600
CE Large monstrous humanoid
Init +2; Senses darkvision 60 ft., Perception +20
Defense
AC 23, touch 12, flat-footed 20 (-1 size, +2 Dex, +1 dodge, +8 natural, +2 shield)
hp 126 (12d10+60)
Fort +10, Ref +10, Will +11
DR 5/magic and adamantine; Immune cold, petrifaction
Defensive Abilities all-around vision, fortification (25%)
Offense
Speed 50 ft.
Melee scimitar +17/+12/+7 (1d6+6/18-20 plus blackfire blade), 2 hooves +12 (1d4+3), snakebite +12 (1d4+3 plus poison) or snakebite +17 (1d4+6 plus poison), 2 hooves +12 (1d4+3)
Ranged masterwork composite longbow +14/+9/+4 or +12/+12/+7/+2 (1d8+6/x3 plus blackfire blade and poison)
Space 10 ft.; Reach 5 ft.
Special Attacks gaze
Statistics
Str 23, Dex 14, Con 21, Int 10, Wis 16, Cha 15
Base Atk +12; CMB +19; CMD 32 (36 vs. trip)
Feats Dodge, Mobility, Point Blank Shot, Precise Shot, Rapid Shot, Spring Attack
Skills Acrobatics +11 (+15 when jumping), Craft (bows) +12, Intimidate +14, Perception +20 Survival +16; Racial Modifiers Perception +4
Languages Common, Sylvan
SQ martial training, poison use, undersized weapons
Ecology
Environment temperate forests
Organization solitary or family (2-3)
Treasure standard (heavy steel shield, scimitar, masterwork composite longbow [+6 pull], 40 arrows, other treasure)
Special Abilities
Blackfire Blade (Su) Any manufactured weapon wielded by a chaeronyx is limned in black flames. A living creature struck by a manufactured weapon wielded by a chaeronyx takes an additional 1d6 damage and must succeed a DC 18 Fortitude save or take 1 point of Strength damage. An undead creature struck by a blackfire blade takes no additional damage, but must succeed a DC 18 Will save or be panicked for 1d4+1 rounds. The save DC is Charisma based.
Gaze (Su) Turn to stone permanently, 30 ft., Fortitude DC 18 negates. The save DC is Charisma based.
Martial Training (Ex) A chaeronyx is proficient in all martial weapons and shields, except tower shields.
Poison (Ex) Bite—injury; save Fort DC 21; duration 1/round for 6 rounds; effect 1d3 Str damage; cure 1 save. The save DC is Constitution based.
Poison Use (Ex) A chaeronyx can apply poison to its weapons without a chance of the poison being wasted.
Undersized Weapons (Ex) A chaeronyx uses weapons as if it were one size category smaller than its actual size.