Trees of Prophecy
Swarm Template (Elite Soldier)
Vulnerability 10 close and area attacks.
Saving Throws +2
Action Point 1
Hit Points +8 per level + Constitution score
The creature gains the Swarm keyword.
Size increases by two steps (tiny > medium, small > large, medium > huge, large > gargantuan). Reach remains the same as that of the original creature.
Mounted creatures can be turned into swarms. Use the size of the mount (usually large) to determine the swarm’s new size. Use the mount’s speed to determine the swarm’s speed.
Aura; the swarm makes a basic melee attack as a free action against each enemy that begins its turn in the aura. The aura’s range equals the reach of the original creature.
A swarm takes half damage from melee and ranged attacks. It is immune to forced movement (pull, push and slide) caused by such attacks.
The swarm can enter or move through an enemy’s space; this movement does not provoke opportunity attacks. An enemy can enter a space occupied by a swarm, but the space occupied by the swarm is considered difficult terrain, and doing so provokes an opportunity attack. A swarm can squeeze through any opening large enough to accomodate even one of its constituent creatures, i.e. it counts as two sizes smaller for the purpose of squeezing.
source is ENWorld