Ayperobos Swarm (CR 12)

Diminutive Outsider (Swarm)
Alignment: Always lawful evil
Initiative: +11(+7 Dex, +4 Improved Initiative); Senses: scent, see in darkness, Listen +18, and Spot +18
Languages: Celestial, Draconic, Infernal; telepathy 100 ft.

AC: 25 (+4 size, +7 Dex, +4 natural), touch 21, flat-footed 18
Hit Dice: 13d8+13 (71 hp); DR: 10/good or silver
Fort +9, Ref +15, Will +10
Speed: 5 ft. and Fly 90 ft. (perfect)
Space: 10 ft./0 ft.
Base Attack +13; Grapple -
Attack: Swarm
Damage: 2d6 plus disease
Special Attacks/Actions: control body, disease, distraction, summon baatezu
Abilities: Str 1, Dex 24, Con 13, Int 8, Wis 15, Cha 13
Special Abilities: control body, disease, distraction, summon baatezu; Immune to fire, poison, swarm immunities; Resist acid 10, cold 10; SR 25
Special Qualities: swarm traits, regeneration 3
Feats: Ability Focus (disease), Ability Focus (distraction), Dodge, Improved Initiative, Mobility,
Skills: Hide +35, Intimidate +17, Knowledge (the planes) +15, Listen +18, Search +15, Spot +18, and Survival +18 (+20 on other planes or to follow tracks)
Advancement: -
Climate/Terrain: Almost always in Maladomini (Nine Hells of Baator)
Organization: Swarm
Treasure/Possessions: -

Source: Fiendish Codex II

Regeneration (Ex): Silver, good-aligned weapons, and spells or effects with the good descriptor deal normal damage to an ayperobos.

Disease (Ex): Devil chills - swarm, Fortitude DC 19, incubation 1d4 days, damage 1d4 Str. The save DC is Constitution-based. It takes three, not two, successful saves in a row to recover from devil chills.

Control Body (Ex): An ayperobos swarm automatically burrows into the flesh of any creature that is within its space and fails a Fortitude save to resist becoming distracted (see below). The swarm is removed from play as it takes control of the victim's body. This ability functions like the dominate monster spell. Each round, the subject gains a new Fortitude save to expel the swarm from its body. Should the subject succeed, the swarm leaves the victim's body and occupies the same space it did before seizing control, filling a 10-foot square that must include the subject. Those creatures that eject the swarm also resist the distraction effect for that round.

Distraction (Ex): Any creature vulnerable to an ayperobos swarm's damage that begins its turn with a swarm in its square is nauseated for 1 round and must save against the control body ability; a DC 19 Fortitude save negates the effect. Even after a successful save, spellcasting or concentrating on spells within the area of a swarm requires a Concentration check (DC 19 + spell level). A creature trying to use a skill that requires patience and concentration must make a successful DC 19 Concentration check to do so. The save DC is Constitution-based.

Summon Baatezu (Sp): Once per day, an ayperobos swarm can attempt to summon another ayperobos swarm with a 75% chance of success. This ability is the equivalent of a 5th-level spell (CL 13th).

Swarm Subtype

A swarm is a collection of Fine, Diminutive, or Tiny creatures that acts as a single creature. A swarm has the characteristics of its type, except as noted here. A swarm has a single pool of Hit Dice and hit points, a single initiative modifier, a single speed, and a single Armor Class. A swarm makes saving throws as a single creature.

A single swarm occupies a square (if it is made up of nonflying creatures) or a cube (of flying creatures) 10 feet on a side, but its reach is 0 feet, like its component creatures. In order to attack, it moves into an opponent's space, which provokes attacks of opportunity. It can occupy the same space as a creature of any size, since it crawls all over its prey. A swarm can move through squares occupied by enemies and vice versa without impediment, although the swarm provokes attacks of opportunity if it does so. A swarm can move through cracks or holes large enough for its component creatures.

A swarm of Tiny creatures consists of 300 nonflying creatures or 1,000 flying creatures. A swarm of Diminutive creatures consists of 1,500 nonflying creatures or 5,000 flying creatures. A swarm of Fine creatures consists of 10,000 creatures, whether they are flying or not. Swarms of nonflying creatures include many more creatures than could normally fit in a 10-foot square based on their normal space, because creatures in a swarm are packed tightly together and generally crawl over each other and their prey when moving or attacking. Larger swarms are represented by multiples of single swarms. (A swarm of 15,000 centipedes is ten centipede swarms, each swarm occupying a 10-foot square.) The area occupied by a large swarm is completely shapeable, though the swarm usually remains in contiguous squares.

Traits: A swarm has no clear front or back and no discernible anatomy, so it is not subject to critical hits or flanking. A swarm made up of Tiny creatures takes half damage from slashing and piercing weapons. A swarm composed of Fine or Diminutive creatures is immune to all weapon damage.

Reducing a swarm to 0 hit points or lower causes it to break up, though damage taken until that point does not degrade its ability to attack or resist attack. Swarms are never staggered or reduced to a dying state by damage. Also, they cannot be tripped, grappled, or bull rushed, and they cannot grapple an opponent.

A swarm is immune to any spell or effect that targets a specific number of creatures (including single-target spells such as disintegrate), with the exception of mind-affecting spells and abilities (charms, compulsions, phantasms, patterns, and morale effects) if the swarm has an Intelligence score and a hive mind. A swarm takes half again as much damage (+50%) from spells or effects that affect an area, such as splash weapons and many evocation spells.

Swarms made up of Diminutive or Fine creatures are susceptible to high winds such as that created by a gust of wind spell. For purposes of determining the effects of wind on a swarm, treat the swarm as a creature of the same size as its constituent creatures (see Winds, page 95 of the Dungeon Master's Guide). For example, a swarm of locusts (a swarm of Diminutive creatures) can be blown away by a severe wind. Wind effects deal 1d6 points of nonlethal damage to a swarm per spell level (or Hit Dice of the originating creature, in the case of effects such as an air elemental's whirlwind). A swarm rendered unconscious by means of nonlethal damage becomes disorganized and dispersed, and does not re-form until its hit points exceed its nonlethal damage.

Swarm Attack: Creatures with the swarm subtype don't make standard melee attacks. Instead, they deal automatic damage to any creature whose space they occupy at the end of their move, with no attack roll needed. Swarm attacks are not subject to a miss chance for concealment or cover. A swarm's statistics block has "swarm" in the Attack and Full Attack entries, with no attack bonus given. The amount of damage a swarm deals is based on its Hit Dice, as shown below.

Swarm HDSwarm Base Damage
21 or more5d6

A swarm's attacks are nonmagical, unless the swarm's description states otherwise. Damage reduction sufficient to reduce a swarm attack's damage to 0, being incorporeal, and other special abilities usually give a creature immunity (or at least resistance) to damage from a swarm. Some swarms also have acid, poison, blood drain, or other special attacks in addition to normal damage.

Swarms do not threaten creatures in their square, and do not make attacks of opportunity with their swarm attack. However, they distract foes whose squares they occupy, as described below.

Distraction (Ex): Any living creature vulnerable to a swarms damage that begins its turn with a swarm in its square is nauseated for 1 round; a Fortitude save (DC 10 + 1/2 swarm's HD + swarm's Con modifier; the exact DC is given in a swarm's description) negates the effect. Spellcasting or concentrating on spells within the area of a swarm requires a Concentration check (DC 20 + spell level). Using skills that involve patience and concentration requires a DC 20 Concentration check.