Swarm, Ephemeral (CR 5)

Tiny Undead (Incorporeal and Swarm)
Alignment: Usually chaotic evil
Initiative: +4 (Dex); Senses: darkvision 60 ft., Listen +9, and Spot +10


AC: 20 (+2 size, +4 Dex, +4 deflection), touch 20, flat-footed 16
Hit Dice: 12d12 plus 12 (90 hp)
Fort +4, Ref +8, Will +8
Speed: Fly 30 ft. (good)
Space: 10 ft./0 ft.
Base Attack +6; Grapple -
Attack: Swarm
Full Attack: Swarm
Damage: Swarm 1d6 Str
Special Attacks/Actions: Distraction, Strength damage
Abilities: Str -, Dex 18, Con -, Int 2, Wis 11, Cha 18
Special Qualities: half damage from slashing and piercing, incorporeal traits, swarm traits, undead traits
Feats: Alertness; Toughness (4)
Skills: Listen +9 and Spot +10
Advancement: -
Climate/Terrain: Ethereal Plane
Organization: Solitary
Treasure: None

Source: Monster Manual III

A ghostly swarm of rats floats silently and eerily along the ground, creeping closer.

Ephemeral swarms are the ghostly collections of many little creatures that suffered a common death. Just as when a spirit of a particular creature lingers on as a ghost, when many small creatures die a violent death, they may linger on as a vengeful ephemeral swarm. The undead swarm is composed of the psychic agony and anguish of the newly departed.

The physical appearance of the creatures in the swarm corresponds to what was killed. Thus, in an area where a plague killed all the cats, the ephemeral swarm will look like a pack of cats and kittens. If a fireball spell took out a rats' nest, the ephemeral swarm would seem to be a ghostly rat swarm.

Incorporeal Subtype

Some creatures are incorporeal by nature, while others (such as those that become ghosts) can acquire the incorporeal subtype. An incorporeal creature has no physical body. It can be harmed only by other incorporeal creatures, magic weapons or creatures that strike as magic weapons, and spells, spell-like abilities, or supernatural abilities. It has immunity to all nonmagical attack forms. Even when hit by spells, including touch spells or magic weapons, it has a 50% chance to ignore any damage from a corporeal source (except for positive energy, negative energy, force effects such as magic missile, or attacks made with ghost touch weapons). Non-damaging spell attacks affect incorporeal creatures normally unless they require corporeal targets to function (such as the spell implosion) or they create a corporeal effect that incorporeal creatures would normally ignore (such as a web or wall of stone spell). Although it is not a magical attack, a hit with holy water has a 50% chance of affecting an incorporeal undead creature.

An incorporeal creature's natural weapons affect both in incorporeal and corporeal targets, and pass through (ignore) corporeal natural armor, armor, and shields, although deflection bonuses and force effects (such as mage armor) work normally against it. Attacks made by an incorporeal creature with a nonmagical melee weapon have no effect on corporeal targets, and any melee attack an incorporeal creature makes with a magic weapon against a corporeal target has a 50% miss chance except for attacks it makes with a ghost touch weapon, which are made normally (no miss chance).

Any equipment worn or carried by an incorporeal creature is also incorporeal as long as it remains in the creature's possession. An object that the creature relinquishes loses its incorporeal quality (and the creature loses the ability to manipulate the object). If an incorporeal creature uses a thrown weapon or a ranged weapon, the projectile becomes corporeal as soon as it is fired and can affect a corporeal target normally (no miss chance). Magic items possessed by an incorporeal creature work normally with respect to their effects on the creature or another target. Similarly, spells cast by an incorporeal creature affect corporeal creatures normally.

An incorporeal creature has no natural armor bonus but has a deflection bonus equal to its Charisma bonus (always at least +1, even if the creature's Charisma score does not normally provide a bonus).

An incorporeal creature can enter or pass through solid object but must remain adjacent to the object's exterior, and so cannot pass entirely through an object whose space is larger than its own. It can sense the presence of creatures or objects a square adjacent to its current location, but enemies have total concealment from an incorporeal creature that is inside an object. In order to see clearly and attack normally, a incorporeal creature must emerge. An incorporeal creature inside an object has total cover, but when it attacks a creature outside the object it only has cover, so a creature outside with a readied action could strike at it as it attacks. An incorporeal creature cannot pass through a force effect.

Incorporeal creatures pass through and operate in water as easily as they do in air. Incorporeal creatures cannot fall or take falling damage. Incorporeal creature cannot make trip or grapple attacks against corporeal creatures, nor can they be tripped or grappled by such creatures. In fact, they cannot take any physical action that would move or manipulate a corporeal being or its equipment, nor are they subject to such actions. Incorporeal creatures have no weight and do not set off traps that are triggered by weight.

An incorporeal creature moves silently and cannot be heard with Listen checks if it doesn't wish to be. It has no Strength score, so its Dexterity modifier applies to both its melee attacks and its ranged attacks. Non-visual senses, such as scent and blindsight, are either ineffective or only partly effective with regard to incorporeal creatures. Incorporeal creatures have an innate sense of direction and can move at full speed even when they cannot see.

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.