Nightmares would require a little more development, but here are some pointers:

• Nightmares are Aggendi terrorist/spies.  It is the Nightmares who can tap into the Massmind and were awaken by the Massmind once again being activated; or so the belief goes.  Another belief is that the Aggendi placed these spies in their raids as to work from within, but this doesn't explain the high officials who now work for the Aggendi against their will.
• Nightmares differ from other Aggendi/Algolian races as they are not as easily identified.
• Nightmares are able to tap into the Aggendi Massmind to help which ever side they choose to join. 
• Nightmares don't appear until the Aggendi awaken with their Massmind calling to it's troups.  Most (92%) of Nightmares would follow their Imperium gene to be tools of the new Massmind without choice, others (5%) because they they choose to follow the Massmind, but a few (3%) could resist and go against their Imperium to follow the Massmind.  The few Nightmares who resist may be few, but would be keystones in resisting the new Aggendi threat to Algol.
• Nightmare are almost undetectable save for their Imperium Gene which forces these Algolians to obey the will of the Aggendi Massmind.
• Nightmares, are also the new terrorist weapon and only spy network for the Agendi Massmind on Algol!  Nightmares may be unwittingly aiding the Agendi through their ability to tap into the Massmind.
• Nightmares were undetecatable until the Aggendi came out of Hybernation and redundant DNA in the Nightmares then becomes active; setting these people apart, but only because of their imperium to obey the Massmind and ability to joined with it.  Yikes!