Just stopping by to say your Sigma Galaxy has a beautiful paint job.
What kind of battles have they been involved in? (As in fighting, not financing.)
Sigma galaxy is actually a garrison cluster back in the homeworlds. So any sort of trials being waged can involve them. Prior to the great refusal they probably scrap with the Smoke Jaguars the most often since the Jaguars took exception to the way that Clan Diamond Shark treats its lower castes. But any clan can be a good fight.
We actually lose track of Sigma Galaxy after Field Manual updates. But that book has then scrapping with Ice Hellions.
They show up again in Field Manual 3085... and by show up I mean, "They are rumored to exist" which means that they survive the homeworlds fight. Sigma is bigger then,
At that point Rho Spina and Zeta galaxies are gone. Presumably destroyed in the fighting against the Steel Vipers.
If you would like to play Sigma galaxy then one of the best opportunities is the Wars of Reaving.
The Vipers hit Strato-Domingo, Paxon and Babylon in force but the defending forces weren't listed.
Sigma should be there somewhere and after some intial setbacks the Sharks manage to push the Vipers back and pay in blood. Until they unleash their Leviathan Prime which savaged one of our naval stars.
But at least we made them tip their hand and we did it in true shark faction. Pushing Zell to its breaking point and being magnificent bastards.