Weapon and Armor Proficiency: Abyssal Horrors are proficient in all simple and martial weapons and all armor and shields. Abyssal Horrors suffer armor check penalties as normal. Abyssal Horrors tend to abhor shields as they loose the use of some abilities (see below) when doing so. If the demon has Multiattack feat and its primary attack is its claws/hands it can use weapons of its size category or smaller in both hands in place of its natural claw/hand attacks.
Arms of Pain: When a demon becomes an Abyssal Horror its arms increase in length by five feet. The demon now has a bonus 5 foot reach on top of any reach that they may have already had and a +4 natural bonus to Strength. But the draw back to this is the Demon constantly suffers great pain and therefore suffers a -2 to its Intelligence score and a -4 to its Wisdom score. Once the change has taken place there is no going back for the demon. If the demon has more than one pair of arms (such as the Glabrezu or Marilith) only one pair, designated by the DM or at random, grows in length.
Roar of Terror (Su): 1/day an Abyssal Horror can let loose a terrible cry that paralyzes all living creatures within 60 for 1d6 rounds (Fort DC 10 + Charisma Modifier + 1/2 HD). In addition all good aligned creatures within 30 foot of the demon must make a Fortitude save (DC 10 + Charisma Modifier + 1/2 HD) or suffer the effects of Smite Good attack. All Good aligned creatures within range that fail their saving throw take damage equal to the Abyssal Horror's Charisma Modifier + the Abyssal Horror's Class level.
Abyssal Taste (Ex): At 2nd level an Abyssal Horror's tongue becomes long and tough; 5 feet long for each size category of small and above. Tanar'ri smaller than Small size do not gain the increased length. The tongue and mouth are coated with a powerful acid that does not affect the Abyssal Horror. As a full attack the Abyssal Horror can make a ranged touch attack with its tongue in an attempt to grapple or trip opponents (Subject to Attacks of Opportunity. Even if the trip or grapple is opposed, but the attack roll is successful, the acid on the tongue deals 1d6 points of Acid damage. If the demon succeeds on a grapple check and if the demon has a bite attack it then draws the opponent into its square and deals an addition 1d6 points of acid damage.
Bonus Feat: At 3rd level, and every third level after (6th, 9th), an Abyssal Horror gains a bonus feat in addition to feats gained through regular class advancement. Any feat that the Abyssal Horror qualifies for can be taken.
Teleport Other (Sp): Once per day as a standard action, beginning at 3rd level, with an additional attempt at 6th and 9th level, an Abyssal Horror can focus its spell-like ability of teleport without error upon a subject within sight. Targets can only be teleported to a location within 30 feet of the Abyssal Horror and the location must be "safe" (i.e. the Abyssal Horror cannot teleport the target to a point 30 feet above the ground, or over the edge of a cliff, etc.). The target of the spell is allowed a Will saving throw (DC 10 + Charisma modifier + 1/2 HD) to resist. This ability is usually used to draw a fleeing opponent back within reach of the Abyssal Horror. An Abyssal Horror that does not possess the spell-like ability of teleport without error cannot use this ability. If the Abyssal Horror so chooses, and can use this ability multiple times per day (i.e. at 6th or 9th level) it can target a number of creatures up to and including the number of the ability's uses per day as a standard action. Using this ability in this way expends the remaining uses for that day regardless of the number of creatures teleported (i.e. a 9th level Abyssal Horror teleports two opponents back within reach. It cannot use this ability again until the next day even though it could normally Teleport Other 3 times per day). Using this ability does not limit the usual "at will" teleport without error ability of the Tanar'ri.
Ripple Earth (Su): At 4th level an Abyssal Horror gains the ability send a shockwave that disturbs the earth out to 60 feet, centered on the Abyssal Horror. All creatures within range must make a Reflex save (DC 10 + Constitution modifier + 1/2 HD) or fall prone. Structures and Earth elementals within range are subject to 2d8 points of damage per Abyssal Horror Class level (i.e. at 4th level Structures and Earth Elementals take 8d8 points of damage while a 10th level they take 20d8 points of damage.). Earth elementals are allowed a Fortitude save (DC 10 + Constitution modifier + Abyssal Horror Level) for half damage.
Rage of Chaos (Su): At 5th level an Abyssal Horror gains the ability to fly into a chaotic flurry of attacks. This ability can only be used a number of times based on the Abyssal Horror's level (1/day at 5th level, 2/day at 7th level, 3/day at 9th level). As long as the Abyssal Horror is not using a shield, has only weapons that it is proficient with or has its natural attacks and has Multiattack with its claws/hands as its primary weapon it can make two attacks with its Arms of Pain against every opponent within reach at its highest base attack. This attack uses the Full Attack action.
Gaze of the Abyss (Su): At 10th level an Abyssal Horror may make a number of Gaze attacks equal to its Charisma modifier -1 (minimum of one) per day. Any who look upon the gaze must make a Will Save (DC 10 + Charisma modifier + 1/2 HD) or become paralyzed for 2d6 rounds. A paralyzed victim must, at the end of the paralysis, make a Fortitude save (DC 10 + Constitution modifier + 1/2 HD) or fall victim to a terrible disease. The incubation is 1d6 days and the damage is that the victim transforms itself into a Dretch. Once a creature fails its initial save against the disease it must make another save at the same DC at the end of the incubation period or transform into a lowly demon. Should the creature's saving throw succeed at the end of the incubation period the creature does not recover but incubation is renewed for another 1d6 days. The only way to remove the disease during the incubation is through Heal, Mass Heal, Miracle, Remove Disease, Remove Disease, Restoration or Wish spells or other like enchantments. Once the victim has become a Dretch only a Miracle, Wish or other divine-like intervention can return the victim to its natural state. On becoming a Dretch the victim looses all former abilities, classes, hit points, etc. The victim is, in all respects, a Dretch and only fleeting memories of its former self are left.