Messier 33, otherwise known as the Triangulum Galaxy, is the third-largest member of the Local Group of galaxies (which includes the Milky Way and Andromeda galaxies, plus their respective satellite galaxies and orbiting clusters and so forth). In terms of distance, M33 is approximately three million light years away from us; though it's only 570kly or so away from Andromeda. While the currently-published data doesn't state this one way or another, this is probably not a good thing for the Triangulum Galaxy; considering just who is known to operate from their larger galactic neighbour...
In terms of Star Fleet Universe publication, the Triangulum Galaxy is at something of a crossroads. At the present time, playtest data on three empires based in M33 can be found in Star Fleet Battles Module E2 (which is now available on e23); while four ships for another Triangulum power was offered in Captain's Log #23 (also now on e23). Along with these files, a pair of ships for one of three E2 powers was uploaded as a separate playtest PDF; proviisional rules for a new type of unit can be found here; while a special countersheet is also available which includes, among other things, counters for all four of the current batch of playtest empires. To cap things off for the time being, an updated errata file includes the current list of edits and changes to the playtest material.
Reportedly, there was a file submitted to ADB a while back by the Triangulum setting's project designer, Francois Angers; which refines the four current playtest empires, and adds in four others for consideration. However, at this point, the Triangulum Galaxy has yet to be selected for formal publication.
(To give an example of how the process worked for a different setting, the Lesser Magellanic Cloud was once offered as a playtest file in SFB Module E1. Eventually, as the ships and rules for the LMC were playtested and further refined, with more units and forces added in, its "formal" publication came with SFB Module C5; at which point, the E1 material became obsolete. Hopefully, at one point, a similar "full" module may one day bring M33 up to the same level someday.)
To try and put a long story short, the main thing to bear in mind is that M33 is not quite bedded down as a formally-published setting, at least not compared to the LMC or the Omega Octant; however, if you are interested in checking out some of the currently-available material (with the caveat that it may be more prone to change than anything you'd see in the other published settings) you may find enough to help inspire some interest in this particular corner of the universe.
In SFU terms, Triangulum is literally a world apart from most of the settings seen in the Star Fleet Universe thus far. While the LMC and the Omega Octant are each at a remove from the Alpha Octant, there is at least some confirmed contact between them later in the timeline. (Even the M81 Galaxy, much further away from the Milky Way than Triangulum, has a connection to the Alpha Octant courtesy of the Tholians and Seltorians that originally hailed from there.) Triangulum, in contrast, has no direct link to "our" neck of the woods (at least, none that we know about so far); for good or ill, it stands on its own merits, though of course nothing is stopping players from mixing it up with other settings' fleets if they wanted to.
Historically, there were three major threads from the distant past, which have come to overlap in the modern era in many different (and often unexpected) ways.
One major building block was the Old Empire; an enormous realm once run by the mysterious Ancient Ones, whose legacy was benign or malevolent depending on which former subject species you happen to ask. The Old Empire stood for centuries across most of the known region of the galaxy until approximately -Y1000, when a group known as the Saviours (or Usurpers, again depending on who you ask) recruited a number of disgruntled Old Empire subject species and plunged the Old Empire into a devastating civil war. At the war's end, the Empire was shattered, and both the Ancient Ones and Saviors/Usurpers fled to parts unknown; the surviving planets, still divided into rebel and loyalist camps, were forced to spend several centuries trying to establish their own successor states upon the vast carcass of the old one. (Howver, by Y1, even the two largest powers, the loyalist Imperium and the rebel Frigian Kingdom, together only held a fraction of the space the Old Empire had claimed at its height.)
The second, which also took place at around -Y1000, was the establishment of the Helgardian Protectorate in the Triangulum Galaxy. The long-lived Helgardian species had spent ten thousand years building an immense, peaceful realm in their original quantum reality; however, some mysterious process suddenly transplanted their entire home star system, complete with its own Ringworld, deep into an unexplored region of "our" Triangulum Galaxy. After three hundred years spent fruitlessly trying to find a way home, the Helgardians eventually gave up trying, and decided to settle in. At the time, the Helgardians were streets ahead of everyone else (including the Old Empire's successor states) and could have dominated the galaxy if they had been so inclined; however, their low rate of procreation (which allows them to settle only a handful of new colonies every century) coupled with their peaceful-minded outlook meant that they would strive to be no more than the first among equals. So, by Y1, the Helgardian stronghold was by far the most powerful and advanced force in the galaxy; but still had a very long way to go in order to replicate the heights they had managed back in their old dimension.
The third, made possible by the Old Empire's devastating collapse, was the slow rise of a vast array of new species on the Triangulum galactic map. With a vast stretch of unclaimed space lying between the Imperium, Frigians, and Helgardians, and only a bare handful of star-faring enclaves in the midst of all that open territory by Y1, the modern era started with a wide variety of new, young species, on the cusp of making their mark on the galactic stage. Seizing the opportunity to set a good example, the Helgardians offered a series of "Warp Pacts" to several of these emergent planets; granting them the equivalent of Early Years technology (which, though far ahead of what each planet had originally, was still well behind the Helgardians' place on the technology curve) and opening a series of trade routes which the Helgardians hoped would inspire their new protégés into becoming constructive members of the galactic community.
Unfortunately, some things started to happen that the Helgardians had not planned for (and for which the Imperials and Frigians would be less than grateful). Some of the young realms, like the Mallaran Empire, proved to be far more belligerent than the Helgardians had expected them to be; the Mallarans even attempted to attack Helgardian space directly (an act which soon prompted the kind of lesson that taught them, and everyone else, that the Helgardians were not be to crossed.) To compound matters, certain chance events would see warp technology end up in places other than their intended destinations. The most infamous being the case of the Arachnids; a psionically-active parasite species that assimilated the crew of a scout ship sent to study their doomed star system, using their new vessel to escape the nova which destroyed their home world, and to subvert dozens of other species into their Worlds of Union.
But what really shocked the Helgardians was just how quickly the warp technology they had handed out would be reverse-engineered and expanded upon. The Helgardians had expected the younger planets to have the same slow rate of advancement as they themselves went through; instead, the younger powers soon managed to build larger and more powerful ships, new technology types, and even caught up with the Helgardians' modern warp engines by Y120. The Helgardians accelerated the pace of their own technological development as a response to this; but, while they still had a substantial head start in terms of the size and power of their home fleet, they were now, ironically enough, no more than "first amongst equals" in the exact opposite manner to which they had hoped for.
At this point, the published timeline only goes as far as Y122, and the First Great Expansion War (the first large-scale conflict fought with modern warp technology, and the first to include a large number of belligerents on either side); the full scope of Triangulum history is said to extend beyond Y200, something I hope to get to read in a published module sooner or later.
In terms on on-table game mechanics, there are a number of technologies to consider; some shared by several powers, others unique to one specific empire.
Defensively, the four current playtest powers have standard shields, along with one of two additional systems; an secondary rotary shield system (for the Helgardians only) or banks of micro-thin Neutronium armour (for everyone else). Rotary shields are a kind of porous shield system which Helgardian ships can use to bolster a specific shield facing; something which helps to offset the lower-than-average shield levels they have ordinarily. Neutronium armour works differently than standard armour, in that it is placed specifically to protect certain key systems aboard a ship; hull damage would be inflicted normally, but sensitive systems (like weapon mounts or control spaces) have a limited degree of ablative protection from these hemispheric Neutronium armour banks.
Offensively, there are four known phaser-equivalent weapons; graviton beams (exclusive to the Helgardians), linear accelerators (exclusive to the Imperium), proton pulse emitters (common in the "western" quadrant of the galaxy) and pulse phasers (used more in the "eastern" galactic region). Each empire also has its own heavy weapon types; the Helgardians have scatter-shot particle shotguns, the Imperium operates turret-mounted hypermass autocannons, the Mallarans use direct-fire plasmatrons and seeking Ram torpedoes, while the Arachnids have plasma-like hellfire and hellblazer technologies.
In addition, there are some quirks and options available here and there. The Helgardian crews are a little better at shrugging off crew casualties; both they and the Imperials can opt for battle armour (which acts as a sort of ablative armour for their Marine squads); the Mallarans operate with a Hydran-esque "casual carrier" doctrine, though with only a handul of Viper fighters flown off any given ship; while the Arachnids have the ability to assimilate many other species directly (though not the Helgardians, who are immune; something which has sharply coloured the Arachnids' opinion of that particular species).
In all, the Helgardian Protectorate, the Mallaran Empire, and the Arachnid Worlds of Union are in Module E2, while the Imperium has a four-ship preview in CL23. The four other powers noted as being in the unpublished playtest mix (the Frigian Kingdom, the Human Republic*, the Atrean Directorate and the Valorean Coalition, if I'm not mis-remembering the old post on the matter) would hopefully have their own particular aspects to consider also, should we ever get to see those powers added in later.
Unlike the other threads, I'm not going to go all-in to try and offer a complete set of weapon or rule ideas. (And not just because I'm drawing a blank with some of them, honest...)
Some of the concepts might take a little time before a good baseline in the official ruleset can be drawn.
For example, the way in which ACtA:SF may handle weapons which in SFB and FC can fire more than once a turn (such as Seltorian particle cannons) would help set a precedent for the likes of Helgardian graviton beams; or even Imperial hypermass autocannons (which technically only fire each chamber once a turn, but have a rule requiring a minimal four-SFB-impulse delay between the firing of each chamber).
Also, if the Hydrans come along with their handy Stingers in tow, the way the rules would govern their trademark casual carrier doctrine would be of direct relevance to how the Mallaran Empire's Viper fighters could (or rather, should) be handled.
So, my personal intention, such as it is, would be to leave this one as a more slow-burning thread; with ideas added to it on a more step-by-step basis, and without a pre-packaged set of unofficial rules offered up-front (the way I did in the Magellanic Cloud thread).
Of course, if anyone reading this has a better sense of how best to adapt this peculiar setting to the ACtA:SF game engine, I would gladly welcome any comments, suggestions, and so forth you may feel inspired to create.
Ultimately, I would have to admit that, even compared to most of the other non-Alpha settings out there in print form, Triangulum may be the furthest away from being viable. Not only would it need at least one formally-published module to work off of, it would take more of a leap of faith into the unknown than either Omega or the LMC (given the setting's further degree of removal from the Alpha Octant compared to those two alternatives).
Still, I personally believe that M33 has a lot of potential; and hopefully, by the time ACtA:SF has expanded to fill out the bulk of the Alpha setting, there could possibly be time to get the setting off the ground in SFB... if enough people want it to be, I guess.
So, to sum up for now; do any of you think that the Star Fleet Universe take on the Triangulum Galaxy is something you may one day like to see make an impact in A Call to Arms: Star Fleet; and if so, how would you rank the idea compared to other non-Alpha settings (Omega, LMC) in terms of which one you would personally want to delve into the most?
*Yes, there are Humans in the Triangulum Galaxy. A convoy of pre-warp colony ships were sent out in the years prior to First Contact; a space anomaly transferred them to the Triangulum Galaxy in -Y12. These Humans (who had never herd of Vulcans or Andorians, let alone Romulans or Klingons) would sign a Warp Pact with the Helgardians in Y14, and develop their warp technology in a wholly different manner to their counterparts back in the United Federation of Planets (or over in the Federal Republic of Aurora, for that matter). As of this point, there is no way to know if anyone in the Federation (or Federal Republic) ever finds out about the Humans of Triangulum; which may raise the question as to where the portion of the "data tapes" concerning M33 was originally sourced...