Dretch Megaswarm

A roiling mass of rubbery skin and flailing limbs surges towards you. Demonic eyes stare at you above slack, fang-filled mouths. This horde is comprised of small creatures with pale, hairless hide compressed so close together that it is difficult to tell where one of these rabid monstrosities ends and the next one begins.
 

Dretch Megaswarm (CR 12)

Small Outsider (Chaotic, Demon, Evil, Extraplanar, Megaswarm)
Alignment: Chaotic Evil
Initiative: +4
Senses: Darkvision 60 feet; Perception +25
  Speed: 20 feet
Space: 10 feet
 

Defense

Armor Class: 15, touch 12, flat-footed 13 (+1 dodge, +3 natural, +1 size)
Hit Points: 136 (16d10+32 plus 16)
Saving Throws: Fort +14, Ref +7, Will +12
half damage from piercing weapons
Damage Reduction: 5/cold iron or good
Immunity: electricity, poison
Energy Resistance: acid 10, cold 10, fire 10
 

Offense

Melee: swarm (6d6)
Reach: 0 feet
  Special Attacks: Distraction (DC 20), feral rage, smite good
 

Statistics

Str	Dex	Con	Int	Wis	Cha
12 (+1)	10 (+0)	14 (+2)	5 (-3)	11 (+0)	11 (+0)

Base Attack Bonus: +16
CMB -
CMD -
  Feats: Dodge, Endurance, Great Fortitude, Improved Initiative, Iron Will, Lightning Reflexes, Skill Focus (Perception), Stealthy, Toughness
  Skills: Escape Artist +20, Perception +25, Stealth +23
  Languages: Abyssal (cannot speak telepathy 100 ft. (limited to Abyssal-speaking targets)
 

Special Abilities

Feral Rage (Ex)

Dretch megaswarms attack in a mindless mob intent only tearing apart those that fall into their clutches. This frenzy prevents them from using any of their regularly-available spell-like or summoning abilities. However, the wild abandon of their attack allows them to deal 6d6 points of damage to any creature whose space they occupy at the end of their move rather than the 4d6 typical for a swarm of their HD. This ability is lost if the swarm is broken up.

Megaswarm Traits (Ex)

Megaswarms are not so called because of the size of the swarm but rather the size of the creatures that compose the swarm. Unlike normal swarms, megaswarms are composed of Small creatures which are usually a megafauna version of a normal swarm and otherwise behave in a swarmlike manner. There are usually around 100 creatures in a megaswarm. The net effect is that they take only half damage from piercing weapons but take normal damage from other weapons. In addition when the swarm is reduced to 0 hit points or lower and breaks up, unless the damage was dealt by area-affecting attacks, then 2d6 surviving members of the megaswarm continue their attack, though now only as individual creatures. Otherwise, a megaswarm conforms to all of the other swarm traits as described in the Pathfinder RPG Bestiary.

Smite Good (Su)

The collective chaos and evil concentrated in the existence of a dretch megaswarm allows the swarm deal extra damage equal to its HD (+16) once per day against a good foe. This ability is lost if the swarm is broken up.
 

Ecology

Environment: Any
Organization: solitary, pack (2-4 megaswarms), infestation (7-12 megaswarms)
Treasure: none

  The lowly dretch are the most moblike of the demons and in certain crowded conditions actually develop a pack mentality and form a swarm. In their rabid mob, dretch swarms lose their ability to communicate with others telepathically, though they can still receive the telepathic commands of other demons to guide them in their attacks. If the swarm breaks up, then surviving dretches continue their attacks, though now as individual creatures regaining their normal abilities and tactics (see Pathfinder Roleplaying Game Bestiary) and losing their feral rage.
  Like individual dretches, dretch megaswarms rely on their sheer numbers when attacking. Unlike individuals, though, megaswarms are not cowardly and attack in a maddened frenzy regardless of the damage they are taking or the stoutness of the adversity. Their own mob mentality prods them on so that the commanding presence of a more powerful demon is not required to motivate them.
  A dretch megaswarm's natural attacks are treated as chaotic-aligned and evil-aligned for the purpose of overcoming damage reduction.
  Credit Original author Greg A. Vaughan Originally appearing in Slumbering Tsar (© Frog God Games/ Greg A. Vaughan, 2012)