The Aeternum Flamma, EVERYBODY LIVES! Deeply emotional preservers of foreign cultures, silicone (not carbon) based 'Rock creatures', that are always on fire, and burn brighter and bigger when feeling more emotion. 

     LORE

        Hailing from a Volcanic world, they are beings of feeling above all, with submissive body-language a la Japan. They are artists and collectors,  they would treat a Poetry contest like we treat Olympics. The idea of lost emotion, lost flame (they burn brighter the more emotional), drives them to despair. They are driven to make sure that no emotional tale, evocative art, or interesting personality, is lost forever. When deprived of emotional stimulation, they literally slow down, physically and mentally, resembling a walking ember. As they can get tired of repeating the same experiences, they are driven to mingle with other species. So emotional are they however, that a communal guilt over declaring war makes them detached from cultures they themselves conquered. Nontheless, when they burn bright, they can throw fire to great effect. Just don't ask them to get off the couch and do it in someone else home.

    GAMEPLAY:

     The game-play style of the Aeternum Flamma is about Builder game style, but also carefully exploring the galaxy (these mechanics encourage you to explore settle far flung corners), and forming strong alliances. 

    Pop Bonus:

       Do onto Others: Each Flamma population unit adds a production bonus for each trade route on system, for the owner and the trade partner.

    Faction Affinity: 

Hearth of All: They receive passive bonuses based on the number of (discovered) races that are currently alive/independent, with bigger bonuses for Empires and smaller but adding up bonuses for minor factions. These accumulate or decrease to include:

     Defensiveness of planets, a Flamma empire which has been allowed to explore the entire galaxy before factions are gobbled up, will be tougher to invade. The bonus helps ground troops fight better on defense only, and makes them more resistant to bombardment.

     Building Production Bonus, because they move faster and spend less time moping, quenched Flamma can work on their second pastime: Charity/civil service, represented by building construction speed increase.

Declaring war removes this bonus from that faction for the rest of the game. Being declared on, doesn't.

Traits:

+A Flame in the Night: Can donate Hearthposts to minor factions, some distance from the Flamma's own borders, to make them tougher for other factions to BOTH conquer, or, influence, their population (fortress, cultural center, and hospital). Each one of these maintained gives +1 influence  to the nearest Flamma system.

+Happy Camper: Flamma ships automatically repair slowly in friendly foreign systems, encouraging alliances, even while moving. (or extra repair if factions do that already)

+Social Frontier: A system/planet receives a FIDS bonus for each independent major and minor faction directly adjacent (or in the constellation if there are never more than a couple node connections)

-Superstitious:  Temporary Speed Penalty upon entry to a new constellation for all (of that Flamma player's) ships, that enter that region. Regardless if maps were traded for or diplomatic relations/access. This helps balance the ease of gathering up the bonus. 

Unique Technologies: 

      Formal Exchange Programs: Each alliance gives a percentage discount to diplomatic actions.

      Mass Hospitality : Allows construction of Refugee Centers building/improvement, which increase propaganda production, and get an additional bonus for each  empire that shares a border with the FLamma that is currently fighting a war.

      Tapping Media Broadcasts: Unlocks Quenchstealer-post building/Improvement,which increases hostile diplomatic demand costs within a large radius, as well as providing line of site greater than normally available.

Note: If you're having trouble visualizing them, think the Rock Monster from Galaxy Quest, covered in flames along the color spectrum for a general idea.

Sure, I was vague about that because I am not too familiar with the game mechanics, but here are my instincts (assuming designers don't just opt for a FIDS bonus):

Defensive passive bonus: With a lot to live for and a lot of literal fire to throw around individually, satisfied Flamma's planets are tougher to conquer (assuming conquering planets is a fight rather than just nuking from orbit; if the latter, they are rock creatures so they should have resistance due to being fine underground and not as easily effected by radiation/chemical weapons as other perhaps.) The lore reason for not having the bonus if it's just bombardments, is being depressed/praying under a bed instead of reacting.

Production passive bonus: If they slow down when not satisfied, than, they move faster when satisfied (and they are rocks so they know their way around minerals, if not pouting in a corner un-quenched). This also pushes them towards a development/builder style. It may make sense to restrict this bonus to buildings, though if there arent good buildings/space stations buildable to purely defend a planet they may need the bonus to apply to fleets.

Basically the game-play idea is to have a weak at the start faction (because the bonus has added up to little), but strong at the mid-or-late game faction (if you go out there and explore/make deals). Both of these bonuses incentivize strong, aggressive powers to target Aeterna Flamma first if they are wise. Because their planets will be harder to conquer if they don't hurry , and because they will have buildings built up to help them compete.