Right, long answer to a short question. Brioc's cast the 3.5 version of the Summon Swarm spell. It summons a swarm of creatures for a duration equal to Concentration + 2 rounds. Given that he's been wounded, he's going to need to make a Concentration roll, but even if he fails the swarm will stay in existence for another 2 rounds.
Summon swarm is treated rather differently under 3.5 rules, due to the addition of the Swarm creature type. While bats individually deal no damage, in a swarm they deal 1d6 points a round, with no attack roll needed. I've copied full details for both the Summon Swarm spell, and the Swarm creature type below. (Both are taken from the 3.5 SRD.)
Summon Swarm
Conjuration (Summoning)
Level: Brd 2, Drd 2, Sor/Wiz 2
Components: V, S, M/DF
Casting Time: 1 round
Range: Close (25 ft. + 5 ft./2 levels)
Effect: One swarm of bats, rats, or spiders
Duration: Concentration + 2 rounds
Saving Throw: None
Spell Resistance: No
You summon a swarm of bats, rats, or spiders (your choice), which attacks all other creatures within its area. (You may summon the swarm so that it shares the area of other creatures.) If no living creatures are within its area, the swarm attacks or pursues the nearest creature as best it can. The caster has no control over its target or direction of travel.
Arcane Material Component: A square of red cloth.
SWARM
Swarms are dense masses of Fine, Diminutive, or Tiny creatures that would not be particularly dangerous in small groups, but can be terrible foes when gathered in sufficient numbers. For game purposes a swarm is defined as a single creature with a space of 10 feet—gigantic hordes are actually composed of dozens of swarms in close proximity. A swarm has a single pool of Hit Dice and hit points, a single initiative modifier, a single speed, and a single Armor Class. It makes saving throws as a single creature.
Many different creatures can mass as swarms; bat swarms, centipede swarms, hellwasp swarms, locust swarms, rat swarms, and spider swarms are described here. The swarm’s type varies with the nature of the component creature (most are animals or vermin), but all swarms have the swarm subtype.
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 large swarm is completely shapeable, though it usually remains contiguous.
COMBAT
In order to attack, a single swarm moves into opponents’ spaces, which provokes an attack of opportunity. It can occupy the same space as a creature of any size, since it crawls all over its prey, but remains a creature with a 10-foot space. Swarms never make attacks of opportunity, but they can provoke attacks of opportunity.
Unlike other creatures with a 10-foot space, a swarm is shapeable. It can occupy any four contiguous squares, and it can squeeze through any space large enough to contain one of its component creatures.
Vulnerabilities of Swarms
Swarms are extremely difficult to fight with physical attacks. However, they have a few special vulnerabilities,
as follows:
A lit torch swung as an improvised weapon deals 1d3 points of fire damage per hit.
A weapon with a special ability such as flaming or frost deals its full energy damage with each hit, even if the weapon’s normal damage can’t affect the swarm.
A lit lantern can be used as a thrown weapon, dealing 1d4 points of fire damage to all creatures in squares adjacent to where it breaks.
BAT SWARM
Diminutive Animal (Swarm)
Hit Dice: 3d8 (13 hp)
Initiative: +2
Speed: 5 ft. (1 square), fly 40 ft. (good)
Armor Class: 16 (+4 size, +2 Dex), touch 14, flat-footed 12
Base Attack/Grapple: +2/-
Attack: Swarm (1d6)
Full Attack: Swarm (1d6)
Space/Reach: 10 ft./0 ft.
Special Attacks: Distraction, wounding
Special Qualities: Blindsense 20 ft., half damage from slashing and piercing, low-light vision, swarm traits
Saves: Fort +3, Ref +7, Will +3
Abilities: Str 3, Dex 15, Con 10, Int 2, Wis 14, Cha 4
Skills: Listen +11, Spot +11
Feats: Alertness, Lightning Reflexes
Environment: Temperate deserts
Organization: Solitary, flight (2-4 swarms), or colony (11-20 swarms)
Challenge Rating: 2
Treasure: None
Alignment: Always neutral
Advancement: None
Level Adjustment: -
A bat swarm is nocturnal, and is never found aboveground in daylight.
Combat
A bat swarm seeks to surround and attack any warm-blooded prey it encounters. The swarm deals 1d6 points of damage to any creature whose space it occupies at the end of its move.
Distraction (Ex): Any living creature that begins its turn with a swarm in its space must succeed on a DC 11 Fortitude save or be nauseated for 1 round. The save DC is Constitution-based.
Wounding (Ex): Any living creature damaged by a bat swarm continues to bleed, losing 1 hit point per round thereafter. Multiple wounds do not result in cumulative bleeding loss. The bleeding can be stopped by a DC 10 Heal check or the application of a cure spell or some other healing magic.
Blindsense (Ex): A bat swarm notices and locates creatures within 20 feet. Opponents still have total concealment against the bat swarm (but swarm attacks ignore concealment).
Skills: A bat swarm has a +4 racial bonus on Listen and Spot checks. These bonuses are lost if its blindsense is negated.