Archives of Nethys

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Creatures in "Hook Fly" Category

Giant Hook Fly2
Hook Fly Swarm1

Hook Fly, Giant Hook Fly

This enormous, horrifically bloated fly has a proboscis shaped like a serrated hook. Its many-faceted eyes smolder like hot coals.

Giant Hook Fly CR 2

Source Gallows of Madness pg. 60
XP 600
N Small vermin
Init +1; Senses darkvision 60 ft.; Perception +0


AC 14, touch 12, flat-footed 13 (+1 Dex, +2 natural, +1 size)
hp 19 (3d8+6)
Fort +5, Ref +2, Will +1
Immune mind-affecting effects


Speed 20 ft., fly 60 ft. (average)
Melee bite +3 (1d4 plus attach)
Special Attacks death throes, spawn brood


Str 11, Dex 13, Con 14, Int —, Wis 11, Cha 2
Base Atk +2; CMB +1 (+9 grapple when attached); CMD 12 (20 vs. trip)
Skills Fly +3


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

Special Abilities

Attach (Ex) When a giant hook fly hits with a bite attack, it latches onto the target, anchoring the target in place. An attached hook fly is effectively grappling its prey. The hook fly loses its Dexterity bonus to AC and has an AC of 13 (touch 11), but holds on with great tenacity and inserts its proboscis into the grappled target’s flesh. A giant hook fly has a +8 racial bonus on combat maneuver checks to maintain its grapple on a foe once it is attached. An attached hook fly can be struck with a weapon or grappled itself; if its prey manages to succeed at a grapple combat maneuver check or Escape Artist check against it, the hook fly is removed.

Death Throes (Ex) If a giant hook fly dies after draining blood with its spawn brood ability but before disgorging a hook fly swarm, its swollen abdomen bursts, sending dead hook flies in every direction. Their tiny hooks deal 2d4 points of slashing damage to all creatures within 10 feet. A successful DC 13 Reflex save halves the damage. The save DC is Constitution-based.

Spawn Brood (Ex) A giant hook fly drains blood at the end of its turn if it is attached to a foe, dealing 1d2 points of Constitution damage. When a giant hook fly drains blood, its abdomen becomes bloated as it spawns an enormous brood of young. It gestates these flies in its abdomen until it has dealt 6 points of Constitution damage with this ability. The following round, the giant hook fly detaches from its victim, and as a standard action that provokes attacks of opportunity, its abdomen ruptures and disgorges a hook fly swarm. The swarm appears adjacent to the giant hook fly and immediately attacks any nearby foes (it ignores the giant hook fly that spawned it). When its abdomen ruptures, the giant hook fly takes 3d6 points of slashing damage. Blood stored in a giant hook fly’s abdomen is absorbed after 24 hours and cannot be used to spawn a brood.


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.