Archives of Nethys

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Creatures in "Hook Fly" Category

Giant Hook Fly2
Hook Fly Swarm1

Hook Fly, Hook Fly Swarm

The tiny, buzzing insects that make up this cloud have distinctive bloated bodies and sharp, if miniscule, proboscises.

Hook Fly Swarm CR 1

Source Gallows of Madness pg. 60
XP 400
N Diminutive vermin (swarm)
Init +1; Senses darkvision 60 ft.; Perception +0


AC 15, touch 15, flat-footed 14 (+1 Dex, +4 size)
hp 11 (2d8+2)
Fort +4, Ref +1, Will +0
Defensive Abilities swarm traits; Immune mind-affecting effects, weapon damage


Speed 10 ft., fly 30 ft. (average)
Melee swarm (1d6 plus bleed and distraction)
Space 10 ft., Reach 0 ft.
Special Attacks bleed (1), distraction (DC 12)


Str 1, Dex 12, Con 12, Int —, Wis 11, Cha 1
Base Atk +1; CMB —; CMD
Skills Fly +7
SQ gestate


Environment any
Organization solitary, pair, or cloud (3–6)
Treasure none

Special Abilities

Bleed (Ex) A hook fly swarm is made up of a terrible mass of juvenile giant hook flies that have undeveloped, though still terribly sharp, proboscises. Any creature that takes swarm damage from a hook fly swarm also takes 1 point of bleed damage at the beginning of its turn. This bleed damage does not stack with itself or other bleed effects. Bleeding can be stopped by a successful DC 15 Heal check or through the application of any spell that cures hit point damage.

Gestate (Ex) Hook fly swarms are made up of underdeveloped giant hook flies, which stay in swarm form for 1 week. Afterward, the swarm finds a secluded place and builds around itself a cocoon-like pod, which it stays in for 1d4 days. This pod is roughly 5 feet by 5 feet in size, and has AC 11 and 11 hit points. After this gestation period, 1d6 giant hook flies burst from the cocoon as a standard action, fully formed and with all of a giant hook fly’s abilities.

Giant hook flies are terrifying, overgrown insects that thrive on their victims’ fresh blood. In particular, giant hook flies are known for their rampant breeding and fast gestation period. Their reproduction is tied to the blood they drain from victims; the more blood they drink, the quicker they can expel their young—which are threats on their own.

Giant hook flies and their parasitic broods can be found anywhere, from a nest in an abandoned barn to the depths of a neglected basement to untold stretches of wilderness. Naturally, they are attracted to blood, so any place where blood is spilled can become a hook fly breeding ground. Butchers and livestock farmers, in particular, must stay vigilant against these dangerous pests, as even the sighting of a single juvenile hook fly might herald a terrible infestation just weeks or even days away. Blood cultists, too, sometimes find that giant hook flies and their spawn are unwelcome visitors to their lairs. On more than one occasion, giant hook flies and their swarms have unwittingly driven evil creatures from their hiding places, surreptitiously aiding a populace shocked that the cultists have been operating in their midst the entire time. Left unchecked, giant hook flies can overrun small farms or other rural places where individuals capable of ending these infestations might be scarce.

That said, giant hook flies are not particularly compelled to stay together, even if they were members of the same brood. In the absence of a strong blood scent to follow, a swarm of juvenile hook flies moves randomly until it finds a secluded area in which to build its cocoon. Once the adults hatch, each of the unintelligent vermin drifts aimlessly, seeking the scent of blood. However, once rooted, giant hook fly populations can prove maddeningly difficult to fully eliminate. Rumor has it that swarms can be dispersed only with gouts of flame; otherwise enough juvenile hook flies survive for the swarm to reform—and surviving swarms inevitably build cocoons that yield fully formed and dangerous new giant hook flies. A common rural saying goes, “If you haven’t killed hook flies with fire, you haven’t really killed them at all.”

The process of spawning a hook fly swarm typically kills the swarm’s parent. Those that survive normally live up to another 6 months, but the damage to their abdomens leaves them unable to spawn again. However, tales tell of particularly enormous and resilient giant hook flies that live much longer life spans and take minimal damage from spawning their broods—meaning they can spawn again. Worse, these creatures are said to expel two brood swarms at a time.

Giant Hook Fly Matriarchs

GMs who wish to use more resilient giant hook flies (often called giant hook fly matriarchs) should make the following adjustments.

A giant hook fly matriarch is CR 3. It has a natural armor bonus of +3 (AC 15, flat-footed 14), 4 Hit Dice (26 hp), a +4 attack bonus to its bite attack, a base attack bonus of +3, a CMB of +2 (+10 grapple), and a CMD of 13 (21 vs. trip). Its spawn brood extraordinary ability deals only 1d6 points of slashing damage to it when its abdomen ruptures, and the ability expels two hook fly swarms at a time.

Giant hook fly matriarchs are typically found alone or with other non-matriarch hook flies in places where spilled blood is enormously abundant, such as on or near recent battlefields, at sites of mass tragedy, or the like. Although they tolerate other giant hook flies, particularly their own spawn, giant hook fly matriarchs are often quite territorial, and matriarchs in close proximity often squabble or even fight the death. However, in places where blood is so abundant that the matriarchs don’t need to fight for resources, giant hook fly matriarchs sometimes coexist peacefully, regularly giving birth to enormous broods. The prospect of such a hook fly population explosion is terrifying to most sentient creatures, as it would ensure that no living creature could survive nearby for long.