Medium Aberration, neutral evil
Armor Class 17 (natural armor)
Hit Points 144 (17d8+68)
Speed fly +40, walk +15
Challenge 10
Skills perception +1
Damage Resistances cold; B/P/S
Damage Immunities poison
Condition Immunities charmed, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned
Senses darkvision 60', passive Perception 11
Languages understands Primordial but can't speak
Blood Sense. Can pinpoint by scent the location of creatures that aren't Undead or Constructs within 30' of it.
False Appearance. While motionless indistinguishable from collection of snowflakes whether resting on the ground or carried by natural winds. It loses this trait if it has consumed blood in the last 24 hrs.
Rust Vulnerability. The large amount of iron in its diet makes it susceptible to effects that harm ferrous metal such as the rust monster's Antennae.
Swarm. Can occupy another creature's space and vice versa and flurry can move through any opening large enough for a Tiny crystalline Aberration. Can't regain hp or gain temp hp.
Multiattack. Two Free Bleeding Cuts attacks.
Free Bleeding Cuts. Melee Weapon Attack: +9 to hit 0' 1 tgt in the swarm's space. 27 (6d8) slashing damage or 13 (3d8) slashing damage if flurry has half of its hp or fewer. If target is a creature other than an Undead or a Construct: DC 16 Con save or lose 13 (3d8) hp at start of each of its turns due to a bleeding wound. Any creature can take an action to stanch the wound with successful DC 12 Wis (Medicine) check. Wound also closes if target receives magical healing.
Source: Tome of Beasts 3 · OGL/Open