GM needs help generating a major villain!, Have scenario, need ringleader Options

[Velocity]

Nova and Sunday_Gamer: there's a magical treasure behind the "spoiler" -- it's wonderful, just click the link and all of your character's accumulated Karma magically vanishes! Isn't that something? :D

To the rest of you:

[ Spoiler ]

I'm running an 'aquadome shutdown' soon and I need some help. Essentially it'll be a version of the arcology shutdown, but with a different origin--what's a good biological version of Deus? Essentially i'm looking for a critter that's capable of some of the same kinds of things that Deus was: mass mind control, generating a hive-like fortress, seeping into every facet of a closed community, generating nigh-limitless numbers of generic--though nasty--shock troops, etc.

Ultimately, it should be on a somewhat smaller scale than Deus, as this will have a much smaller impact on the Sixth World than the AI did.

I've already thought of Vampires (and other HMHVV-related bogeymen) and insect spirits, but those are both a little overdone (IMHO). Any other suggestions? Thanks in advance...