So, for some reason, the original thread discussing the third race is closed (Too old, perhaps), and now having finished the Genesis Campaign, I'm super curious as to what it could be. Now, we already have a little bit of information about them, which is as follows:

Quote from Frogboy: "The PHC and the Substrate are both from Earth.  The third race does not come from Earth."

With that, we can infer one of two things: They're either total aliens, or the Martian humans who rebel in the events of Genesis. However, the latter option seems improbable, given that they would've come from Earth at some point. They are almost assuredly not it, given evidence in later posts. This means the third race is expected to be decidedly alien in nature.

The planet Haalee takes from Mac in Genesis is "haunted".

Mac refuses to convert one of his planets, claiming it is "haunted" by something within it. From that, we can assume one of two possibilities: He didn't want to convert the planet because of a random superstition, or because he felt that the entity within it would benefit from it. It is worth noting, that when Haalee takes over the planet, she also elects not to convert the planet to Turinium, and Haalee has some knowledge of the group in question.

It is also worth noting that both of them reference the entity to be odd. Whether this is to be taken literally (Aliens capable of "spectral" actions, like possession or haunting) or figuratively (Aliens capable of burrowing with the planet, or projecting themselves to lifeforms) remains to be seen.

Haalee has some knowledge of them, the PHC do not.

The fact that Haalee somehow knows of them while the PHC do not raises some interesting questions, because we're never told that Haalee has encountered them on any of her planets, but we know for sure they were present on at least one PHC planet. Now, the PHC are very close to AI already (Being entirely virtual, and extremely intelligent), but seem to possess the same hubris and greed of normal humans. It's also worth noting that no PHC is remotely close to being as intelligent as Haalee, who has managed to fight the entirety of the PHC on her own, and does so while preparing for the coming threat.

Despite her awesome power, Haalee seems extremely unnerved by the coming aliens. She wages war against her closest friend to prepare for them, and the threat of Genesis - an AI that grew to threaten her and the PHC combined she saw as more of a distraction than a credible threat.

This tells us very little, but presents some an interesting possibility: They are either AI themselves, or have a specific relationship to AI. This explains why Haalee is aware of them, while the PHC are not, despite living on a planet with them. It could also explain why Haalee is so terrified of them, as perhaps that relationship is a destructive one. She says they're a threat to her and the PHC - but the PHC do not represent all of humanity, far from it. This would also explain their aversion to Turinium conversion - the entity may possibly "dominate" them through their connection with Turinium. It would also explain why Haalee refers to them as the Nemesis - they're a direct rival AI, one more powerful than Haalee is.

They are far and away more powerful than either faction.

Haalee warns Mac that "Nemesis is coming", and suggests that combined they may not be a match for it. Now, whether that refers to the fact Nemesis seems to have an infectious relationship with Turinium - or whether it's referring to strength of arms - isn't revealed. But for the combined might of the two factions to be threatened by it is alarming. The only other entity to do that so far was Genesis, and that was because the PHC didn't want to get involved, and Haalee was distracted. Even then, Genesis was described as an apocalyptic possibility. That puts Nemesis far, far up the scale in terms of threat.

What we know.

• They are not the Martian rebels with the spaceships. We know this because Nemesis is already present on a distant world, and is referred to by a separate title by Haalee.
• They must be completely alien. This is known because they cannot logically be the Martian Humans, and are called such by Frogboy.
• They are capable of hiding themselves. Despite Mac feeling like the planet is "haunted", he's never actually made aware of the fact there's an alien life on it. This is despite sitting on the planet for "quite a while" by Samuel.
• Haalee is aware of them somehow. How isn't revealed, as they seem to hide themselves from the PHC, but she has a tenuous grasp of the coming threat somehow.
• They are a credible threat to the existance of Strong AI and Virtual Humans. We aren't made aware of how, but we do know that Haalee fears for the both of them.

What we can infer.

• They seem to have a parasitic relationship with Turinium. This can be inferred from Mac and Haalee both choosing not to convert the planet Alnilam, as well as the Nemesis being a threat to the factions that utilize Turinium.
• They can seemingly interact with Turinium lifeforms without direct contact. Mac is vaguely aware of something within Alnilam, despite never having met the aliens. Haalee is also aware of them, despite (Presumably) not having met them.
• They are likely to use less "brute force" tactics against the PHC and Substrate. We already know they've managed to hide in a planet for quite some time, so stealth is likely. Plus their interaction with Turinium - which the PHC and Substrate use to control their units - means they likely have some method of either dominating that signal or interfering with it.

What we have no idea about.

• What they actually look like. They could be organic, AI or even ethereal. And all are completely plausible options.
• Why they're coming. Whether they have a fervent hatred of Turinium, whether it's a simple conquest, whether they're fleeing something else... We have no idea as to their motivation.
• The power of their army. We know they're a threat to PHC and Substrate - but that could simply be about cutting them off from Turinium. Whether their army is more powerful, equally as powerful (Likely in the context of multiplayer) or even potentially less powerful is still up for debate.
• How many there are. We know they've been hiding on at least one planet, biding their time. However, whether there's more of them hidden on other worlds, whether they exist "within" the metaverse data itself, whether there's a fleet waiting to arrive... We don't know any of that.
• What will be their interaction with the three factions? We know Haalee considers them a Nemesis, but is that competitive or combative? The PHC seem superstitious and afraid of them, but why? How will the Martians interact with them?
• On that topic, what will happen with the Martians and them? Could they hijack the Martian ships, giving them a means of travel without using Turinium? Will the Martians help contain them as a threat with their fleet? Will they ally with Nemesis to kill their opposition?

Anyways, sound off below with your own information/ideas/theories/hopes!