OK, I fixed the attacks and lowered the CR to 17. I hereby pronounce the Cipactli... completed!
And, as promised, here's the Obsidian Butterfly Swarm that I've been working on.
A swirling cloud of black, faintly translucent butterflies emerges from the chanting spellcaster’s outstretched hand. They make no sound as they fly, except for a faint tinkling like tiny wind-chimes. As they come closer, your eyes catch sunlight glinting off the razor-sharp edges of their wings.
Obsidian butterfly swarms are most frequently summoned by worshipers of Ītzpāpālōtl, the skeletal warrior-goddess of infant mortality, women who die in childbirth, and leader of the tzitzimime star-demons.
Obsidian Butterfly Swarm CR 4
N Fine Construct (Swarm)
Init +2; Senses Darkvision 60 ft.; Lifesense; Low-light vision; Perception +5
AC 20, touch 20, flat-footed 18; (+8 Size, +2 Dex, +0 Natural)
HP 3d10 (16 hp)
Fort +1, Ref +5, Will +3
Defensive Abilities mindless, swarm traits; Immune electricity damage, mind-affecting effects, bleed, disease, death effects, necromancy effects, paralysis, poison, sleep effects, and stunning, weapon damage
Speed fly 30 ft. (average)
Melee swarm (1d6)
Space 10 ft.; Reach —
Special Attacks distraction (DC 11), shred, wounding
Str 3 (-4), Dex 15 (+2), Con —, Int 1 (-5), Wis 14 (+2), Cha 4 (-3)
Base Atk 3; CMB —; CMD —
Feats Lightning Reflexes, Skill Focus (Perception)
Skills Fly +10, Perception +5
SQ construct traits, swarm traits
Environment any temperate or tropical
Organization solitary, pair, flight (3–6 swarms), or colony (11–20 swarms)
Any living creature that takes damage from an obsidian butterfly swarm is nauseated for 1 round; a Fortitude save (DC 11) negates the effect.
Because they actively seek out the warm blood of sacrificial victims to sustain their patroness, an obsidian butterfly swarm notices and locates living creatures within 60 feet, just as if it possessed the blindsight ability.
An obsidian butterfly swarm causes damage to unattended objects in its space each round as though they were creatures, but only if the object has a Hardness score of 5 or less (examples include glass, paper, cloth, rope, leather/hide, and wood).
Any living creature damaged by a obsidian butterfly 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.