Mechanical Benefits of Being a Swarm

[GreatDane]

NUIL, SELOKASH, AND SERA: STAY OUT!


I have a villain coming up in my current campaign that, through bizarre genes and unfortunate magical accidents, is composed entirely of microscopic flying organisms. The villain holds himself in his natural shape out of habit and for the "comfort" of his colleagues (he's hard enough to work with as it is), but I was wondering what the mechanical benefits and drawbacks of being a swarm would/could be.

What I've got so far is a (slowish) fly speed, gaseous form at will, and swarm subtype traits:

Not subject to precision damage or flanking
Immune to weapon damage
Cannot be tripped/grappled/bull rushed or initiate a grapple
Immune to single-target effects (disintegrate, etc.)
+50% damage from area effects
Susceptible to high winds
Able to deal damage by dispersing into swarm and engulfing/distracting a foe

Any other interesting side effects of being a swarm?

[Mystral]

An interesting feature of swarms is that they can squeeze through any crack small enough for a single member of the swarm. And they can hide in walls or other nooks and crannies.

If he's made out of microscopic sized things, he can basically get through anything short of a wall of force.

[Khedrac]

Check out the epic Worm that Walks (http://www.systemreferencedocuments.org/resources/systems/pennpaper/dnd35/soveliorsage/epicNonAbominations.html#worm-that-walks) template - it is basically exactly what you are describing.

[Necroticplague]

Swarms also have the benefit where they aren't strictly relegated to fixed spaces. So if his swarm form is a 10x10x10 form, he can redistribute those 8 cubes in different patterns, instead of being stuck as a 10x10x10 cube, like all other creatures.

[GreatDane]

Thank you everyone for your suggestions! Indeed, Worm that Walks is exactly what I was looking for. Thanks a million, Khedrac.