The Reconstruction/WMG

Moke is the Si'Shra that killed . Furthermore, he is the Tezkhra figure that the Si'Shra worship.
Warning: Massive, massive spoilers ahead. Do not read unless you've gotten the sixteenth character!

When you take him to the Si'Shra Holyland, Tez says that he was killed by something large with a terrible stench. Everyone assumes that it was a Si'Shra, and seeing as the game is subtle like an anvil to the head about Moke being a Si'Shra, they're probably right. Also, Moke is the only party member that Tez recognizes, and there's a memory flash when he sees him. Tez also seems to be suspicious of Moke and wondering about something relating to him, as seen in Moke's sidequest.

As for the second Wild Guess, the Encyclopedia says that the only known record of Tez by the Shra say that he was a foul, poisonous creature whose breath felled even the strongest warriors. It's difficult to tell how much of this is metaphor, in which case it might be covered by his crash-landing. Assuming it isn't, though, Tez doesn't fit that bill at all, as he doesn't seem to ooze an unknown toxic substance and smell like death cooked twice over, unlike our friend Moke. The "raising his arm and blasting the jungle" thing does seem to be Tez using Stardraw Beam, though, unless Moke had a similar spell before getting abducted by the Sikohlon. How Moke got confused with Tez, I don't know.

Also, Father Sikohlon probably abducted Moke somehow (or perhaps it was Mahk? That would make much more sense...) and mind-wiped him or something. The reason he's such a nice guy is because he was raised as a Sikohlon without any memories of being a world-destroying evil god...thing. Maybe.

Dehl's sword dealing slashing damage is actually perfectly justified.
If it dealt Body damage, there would be no way to explain this and it would be a total Wall Banger. But it does not! It deals Soul damage, and since destroying a person's will to fight probably does not involve the same physics as hitting them with a weapon, Dehl can probably give it aspects of sharpness when he's using it. Soul damage is usually magical or ethereal anyway, so presumably he just makes an ethereal/magical weapon (that's actually sharp) using his sword as a medium.

Fortians are the native inhabitants of the planet.
It would explain their affinity for magic. This would make them Human Aliens, though, which the creator seems to be trying to avoid, making this unlikely.
 * Jossed; Word of God says that they're genetically identical to humans, and the only difference between them is cultural.

...Okay, then, how about fih'jik?
Fih'jik are unique to The Reconstruction. They are not seen anywhere in I Miss the Sunrise, despite the fact that galactic exploration has gone on for a long time. They are also highly traditional and religious, which would make sense if they are native to the planet. Of course, since the planet where the game takes place is very highly implied to have been terraformed and planted with settlers, it's likely that there is no 'native' species.
 * As of And Yet It Moves, almost certainly

The above WMG will be Jossed in the next episode of I Miss the Sunrise
Calling it now: The plot of And Yet It Moves will be cat people who specialize in Extension shells appearing out of nowhere and making all the scientists giddy that they found another sentient species, before the cat people start blathering about the Supreme One and how the nonbelievers must be purged.

Kulkumatz was in possession of or exposed to the fifth +ii emitter at some point.
Warning: massive, massive spoilers for the Golden Ending. Do not read unless you've seen it!

In the Golden Ending, says that there are five +ii emitters on the planet that came with him when he crashed. He destroyed one in the Backstory, and deactivates three more in the ending. However, that still leaves one emitter unaccounted for. My hypothesis is that it's the secret to Kulkumatz's longevity. Kulkumatz is incredibly old even by shra standards, and the area in which he lives is in the vicinity of where Tez destroyed the first emitter. It's possible that there was a second emitter nearby that Tez missed (or perhaps he thought he destroyed it in the blast as well?) that Kulkumatz could have been exposed to. It could have been moved later (or even in a different place entirely that Kulkumatz traveled to at some point), since I Miss the Sunrise implies that the radiation has lasting effects even if the emitter is no longer present. Perhaps the emitter is in the shra capital, or in the possession of The Omniscient Council of Vagueness that Moke meets in his sidequest?
 * Possibly Jossed; Word of God says that the only reason Kulkumatz seems so old is because the age scale for shra is inaccurate: due to their horrible treatment in captivity, they don't live as long as they do in the wild. Since Kulkumatz obviously takes good care of himself and isn't subject to those treatments, he's simply able to live out the natural lifespan of a shra.

Moke is half-si'shra.
I Miss the Sunrise shows that hybrids are possible, and Moke is similar to Daszk: he has many of the physical traits of the si'shra (white eyes, enlarged frame), but does not have the same aggressive urges or links to the si'shra culture. It's possible that the Sikohlon took him in after finding him in the wild somewhere, thinking he was an ordinary shra. The reason he doesn't know of his origins is likely because of the Plague rattling up his memory (that or Sikohlon indoctrination). This could relate to the first WMG on the page.

In the final battle, Adi and Cort are not mind-controlled/brainwashed.
Either they honestly believe in or they're too scared of what might happen if they don't swear loyalty to him. Although, the ragged appearance of their Character Portraits implies he has been mistreating them, so it's probably the latter. It could actually be that Cort is the former while Adi is the latter.
 * There's also the question of how could possibly brainwash them in the first place. Boasting aside, he's not actually all-powerful (he doesn't even use any magic).

The Voice Himself is Virgil or the mysterious lacertian that was talking to Ral.
Most likely the former. Although, the Voice being the (presumably) Big Bad of the prequel would certainly be an interesting twist. (This is assuming Virgil doesn't pull a Havan and turn out to be the Big Bad, though!)
 * After the events of episode 3, it seems most likely that the Voice is, since.

Dehl's father made Moke create the Blue Plague.

 * I'm still pretty sure he's a Lesser, and Lessers seem to be more than just "Si'Shra IN SPACE! (before them)". Unless something was revealed about them in Episode 3, which I haven't played yet, we don't know anything about how Lesser metabolism works, but possibly they can manipulate the biological processes in their own body at will. In which case Moke was forced to manipulate microorganisms to carry his Lesser poison.