Gaian Furies are eco-terrorists. They firmly believe that over-mining and overpopulation by sentient races is an affront to nature. They use stealth and swift strikes to take out civilized production facilities of all races. They follow up by using terraforming technology and biology to return a planet to a primal state. Small colonies have been completely wiped out in the outer sectors.

Ships Ideas:
Gaian Lightning-Small, fast, attack ships utilizing jamming technology and weapons to prevent calls for help.

Gaian Earthquake-Large combined Bomber/troop carriers. Designed for colony invasion/eradication.

Fury Firestorm-Medium support vessel, plasma based weapons.

Gaian Mothership-Planetary terraformer and biology habitat ship. Carries multiple flora/fauna samples from other worlds to create a harmonious eco-system.

I imagine the Lightning as a Common NPC, possibly an uncommon. If it's given a special drop, it should be a jammer.
personally I think there should be no drop.
The Earthquake would drop a planetary assault artifact. Perhaps lowering population by 25 percent, not quite as big as the Bio-Vaporizer.
ARRRRGHHH! -75% pop is not cool. Tiny planets would be reduced to 10 pop...
The Fury Firestorm could either be another common or have an artifact that increases damage vs NPC's for a duration. Really, this ship could be versatile. I was just sketching out the roles of the ships.
I say Uncommon, I agree that it should be versatile and give both an attack and defense artifact.
The Mothership should have some sort of terraforming artifact, planetary population building, or even extra crew for your ship due to the cloning/bio-diversity creation devices onboard.
Extremely rare/elite. Maybe an improved terraformer (+2 on each?) I like the crew idea though.
Please, feel free to make suggestions