Alternate Form (Ex) A bone collective can act as a swarm (composed of dozens of posthumes), or it can grant a single member (called an exarch) control, acting as a singular creature. Changing between forms is a swift action. In its non-swarm form, the collective can no longer use swarm attacks, but it can use sneak attack, disarm, and spellcasting, if it has caster levels. It can use its skills normally in either form.
Amalgam (Ex) Multiple individuals can combine themselves temporarily into a single creature, to a maximum of 25 creatures. Each creature beyond the first grants the amalgam 1 Hit Die, and it gains a size category at 9, 12, 18, and 30 Hit Dice. The amalgam has a number of bite attacks equal to the number of bites of all component creatures combined, but only two secondary attacks. If the amalgam drops below 0 hit points, it dissolves, and the damage is divided among the component creatures.
Exposed Nerves (Ex) Whenever a this swarm is at or below half its full hit points, it's individual members become less capable of working together. Its Intelligence score drops to 9 and it loses its spellcasting ability. When at or below one-quarter its full hit points, it becomes effectively mindless and can only use feats that provide a static bonus.
Hive Mind (Ex) All posthumes of a bone collective within 50 miles of their main body constantly communicate. If one is aware of a particular danger, they all are. No posthume in a group is considered flanked unless all of them are. Any bone collective with at least 1 hp/HD (or 18 hp for a standard collective) forms a hive mind, giving it an Intelligence of 14. (This is an exception to the usual swarm rules.) When a collective goes below this hp threshold, it becomes mindless.
Reflexive Dodge (Ex) The constituent creatures of this swarm can dodge attacks, forming holes in the swarm. It gains a +8 dodge bonus to its AC.
Weight of Wings (Su) Creatures affected by the swarm’s distraction effect must also make a DC 16 Will save (Cha– based) or suffer from the effects of hold person. This paralysis only lasts as long as the victim is within the swarm.