Razoreel Swarm (CR 11)

Tiny Magical Beast (Aquatic and Swarm)
Alignment: Always neutral
Initiative: +14 (+10 Dex, +4 Improved Initiative); Senses: blindsense 120 ft., darkvision 60 ft., low-light vision, Listen +2, and Spot +9


AC: 24 (+4 size, +10 Dex), touch 24, flat-footed 14
Hit Dice: 18d10+54 (153 hp)
Fort +16, Ref +23, Will +8
Speed: 10 ft., burrow 10 ft., swim 90 ft.
Space: 10 ft./0 ft.
Base Attack +18; Grapple -
Attack: Swarm (4d6 + 1d6 Con)
Full Attack: Swarm (4d6 + 1d6 Con)
Damage: Swarm (4d6 + 1d6 Con)
Special Attacks/Actions: Constitution damage, distraction, penetrate damage reduction
Abilities: Str 2, Dex 30, Con 16, Int 2, Wis 10, Cha 2
Special Qualities: evasion, immunity to weapon damage, resistance to acid 10, cold 10, and sonic 10, swarm traits
Feats: Alertness; Great Fortitude; Improved Initiative; Improved Natural Attack (swarm); Iron Will; Lightning Reflexes; Stealthy
Skills: Hide +27, Listen +2, Move Silently +19, and Spot +9
Advancement: -
Climate/Terrain: Temperate coastal
Organization: Solitary, pair, school (3-5), or shoal (6-12)
Treasure: None

Source: Web

Combat

A razoreel swarm seeks to surround and attack any living creatures it encounters, and it pursues them for short distances onto shore if necessary. Some rocky beaches are particularly dangerous, for colonies of razoreels dig into the stone under the shore and create dangerous sections of weak stone that collapse when creatures walk over them.

Constitution Damage (Ex): Anyone damaged by a razoreel swarm must make a Fortitude save (DC 22) or take 1d6 points of temporary Constitution damage as well. This save DC is Constitution-based.

Distraction (Ex): Any living creature that begins its turn with a razoreel swarm in its space must succeed on a DC 22 Fortitude save or be nauseated for 1 round. The save DC is Constitution-based.Even with a successful save, spellcasting or concentrating on spells within the area of a swarm requires a Concentration check (DC 20 + spell level). Using skills requiring patience and concentration requires a Concentration check (DC 20). The save DC is Constitution-based.

Penetrate Damage Reduction (Su): Razoreels are supernaturally sharp, and damage done by a razoreel swarm is treated as a magic weapon for the purpose of dealing damage to creatures with damage reduction. This damage also ignores all hardness an object or creature may possess.

Evasion (Ex): If a razoreel swarm makes a successful Reflex saving throw against an attack that normally deals half damage on a successful save, it instead takes no damage.

Swarm Traits: A swarm has no clear front or back and no discernable 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.

Reducing a swarm to 0 hit points or fewer causes the swarm 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 another.

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 effects if the swarm has an Intelligence score and a hive mind. A swarm takes a -10 penalty on saving throws against spells or effects that affect an area, such as many evocation spells or grenadelike weapons. If the area effect attack does not allow a saving throw, the swarm takes double damage instead.

A swarm rendered unconscious by means of nonlethal damage becomes disorganized and dispersed, and it does not re-form until its hit points exceed its nonlethal damage.

Aquatic Subtype

Creatures with the aquatic subtype always have swim speeds and thus can move in water without making Swim checks. An aquatic creature can breathe underwater. It cannot also breathe air unless it has the amphibious special quality.

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
1-51d6
6-102d6
11-153d6
16-204d6
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.