Stirge Swarm
The pinkish cloud, on closer inspection, seems to be made up of tiny, needle-beaked flying creatures, buzzing as they seek warm-blooded prey.

Stirge Swarm (CR 9; XP 6,400)
N Tiny magical beast (swarm)
Init +8; Senses darkvision 60 ft., low-light vision, scent; Perception +13
AC 20, touch 16, flat-footed 16
(+4 Dex, +4 natural, +2 size)
hp 114 (12d10+48)
Fort +12, Ref +12, Will +5
Defensive Abilities half damage from weapons, swarm traits
Speed 10 ft., fly 40 ft. (average)
Melee swarm (3d6 plus blood drain, disease, plus distraction)
Special Attacks blood drain (1d3 Con), distraction (F-DC 20)
Str 3, Dex 19, Con 18, Int 1, Wis 12, Cha 6
Base Atk +12; CMB —, CMD
Skills Fly +13, Perception +13
Feats Improved Initiative, Skill Focus (Perception)
Environment marsh
Organization solitary, cloud (2-4 swarms), blight (7-12 swarms)
Treasure none
Special Abilities
Disease (Ex) Filth Fever—injury; save Fortitude DC 12; onset 1d3 days; frequency 1/day; effect 1d3 Dex and 1d3 Con; cure 2 consecutive saves.

Many adventurers who have plundered dank dungeons and swamp-swallowed temples have come across the pestilential pest known as a stirge—a bloodsucking little flying monster all too common in warm lands. In small flocks they are usually not a problem for a well-equipped party, and conditions in their preferred domains are rarely conducive to the presence of more than two hands’ worth together. When they are, however, such as when a losing army or a hapless work gang, or even a large herd of cattle are lost in their home-swamps, the egg-laden females can produce large numbers of young in a relatively short time. These large congregations of stirges, known as storms (or swarms), rarely last long, as they strip the countryside of blood-bearing creatures, literally eating themselves into famine. Their behavior changes when in these storms, inducing them to an almost hive-mind attitude. This spurs them to much faster and gluttonous movement and feeding – increasing their deadliness tenfold.

JUNGLE STIRGE SWARM (CR +1): Much smaller (diminutive), green-mottled stirges that congregate for massive mating swarms, feeding on blood and laying eggs in the hollows of giant trees. They are immune to weapon damage, and replace [[[Skill Focus]] (Perception) with Toughness.

FERAL MIASMA SWARM (CR +1): These deep-swamp swarms absorb direr diseases, of note, the dreaded malarial fever, ruiner of empires.

On Porphyra
Regions infested by stirges to the point where swarms could occur, there or in adjacent regions includes the Tarn of Pazuzu in the eastern Birdman Mountains, the Mire of Ashael in Simoon, and the Wet Marshes of coastal Avandrool. The jungles of Californ and Red Cliffs occasionally spawn them, as well.