The following contains spoilers on the nature and origin of superpowers in Worm.

It is recommended that you not read further if you do not wish to be spoiled.

(There's technically a RWBY spoiler, too, but most everyone figured it out within a minute of seeing the robot in question, who I'm not even identifying.)

Right, with that out of the way...in a crossover like Shards, what I consider the most problematic part of planning is figuring out how the supernatural powers of the two universes interact. Not only is it difficult to logically consider such things, with what little information we have and the frequency of authors not seeming to have a firm grasp of the limits of given powers, but readers tend to react poorly when they don't understand why things happen. Thus, I have chosen to write on how I see the supernatural powers of Earth Bet and Remnant interacting.

First off, do passengers have Aura? Why not? It is stated that people and animals do, although the Grimm do not. The reason for this is stated to be because Grimm are "the manifestation of anonymity". This and other quotes imply that Aura is based on soul and/or identity; it's uncertain if (say) bricks, trees, or planets have Aura, but passengers and the Entities they spawn from are on the whole more like animals (which are explicitly stated to possess Aura) than inanimate objects. In any case, there is also an advanced robot with Aura; if such an intelligence has enough of a soul to use it as a sword or shield, why wouldn't the passengers?

Second, can passengers' Auras be awakened? We only see humans (well, one human) get their Aura awakened, but we also see a dog be used as a projectile without so much as getting its fur dirty; Aura is the most obvious explanation (unless we want to invoke "the animator didn't want the dog-punter to come off as a complete monster" and leave it at that), so it's pretty clear that non-human Auras can be awakened, presumably by humans. The passengers are pretty deeply integrated with their hosts, changing both body and mind to varying extents; for the purposes of Shards, I've assumed that attempting to awaken the Aura of a parahuman awakens that of the passenger simultaneously if the awakener doesn't try not to (which obviously couldn't happen without knowledge of passengers, the ability to detect them, or ideally both). It should probably go without saying, but I'm also assuming that awakening multiple Auras at once is less efficient than awakening them one at a time.

(I'll take this opportunity to share a headcanon about Aura that doesn't relate directly to superpowers, though it will be coming up in Shards. Essentially, I assume that the amount of Aura one has is not fixed, and can be increased with training or practice, although with diminishing returns. Some people, like Jaune, have naturally higher "Aura capacities"; I've toyed with the idea that Remnan humans have evolved to have higher Aura capacity than Terran humans since it matters to them, but I'm still on the fence about that. Tying back to passengers, awakening multiple Auras at once, whether human or not, decreases their "maximum Aura" at the start but not their natural "Aura capacity"; in a video game analogy, you start at a lower level but once you hit level 10 you have the same number of "hit points".)

Parahumans can do essentially the same things with Aura as non-para humans can—defense, offense, limited sensory abilites, Semblances, possibly transhumanism, etc—but what about their passengers?

1. The passenger is largely part of the host, so the host can draw on the passenger's Aura. (In all cases, I assume the host's Aura is drawn on first if it should make a difference. I also assume that the sum of a newly-awakened parahuman's "passenger" and "host" Aura would be less than what it would be if the parahuman was just a human.)

2. The passenger learns to harness and/or account for Aura. The exact effects of this vary from power to power, but in general I'm planning to keep it minimal. A Thinker power might get more accurate results when dealing with Aura, Semblances, or Dust (another of my headcanons, this one for Worm, is that passengers don't "know" how to deal with anything but mundane forces and other superpowers). Trump powers might work on Aura-based phenonena as well as superpower-based ones (e.g, Hatchet Face would shut down not only superpowers but also Semblances and even more typical use of Aura). Masters and other capes which create things might have those things sustained by the user's Aura, while others with powers that Aura interferes with would get the ability to "pierce" Aura (likely for a "cost" of Aura); as noted, the Aura would first come from the host's Aura, because passengers are dicks. A few might apply their effects to the user's Aura as they do to the user, although since Aura is a manifestation of one's persona, this might have unintended side effects...

3. If it ever came up, the passenger's Aura would probably be used (before the host's, even) to defend against attacks on the passenger itself, say if they were aimed from whatever universe the shard is actually located on.

4. Can passengers get Semblances of their own? Probably, although it won't be easy; finding and using your Semblance seems to require extensive training of one's Aura, and as noted the passenger's Aura isn't likely to get much work. Still, it's not impossible; a parahuman wanting to awaken his passenger's Semblance might try wearing down his personal Aura and training just what remains, if he could distinguish between the two (typical Aura-detecting equipment probably wouldn't), and direct attacks on the physical shard (see #3) would probably also work fairly well. Semblances are implied to reflect the user's personality and/or self-image, however, and neither passengers nor entities really have either. They might build off of the host's Semblance (if any), the same way one's superpower (given by one's passenger) sort of builds off of one's personality; I don't expect passenger Semblances to come up for a while or be a significant part of the story once they do.

Now, aren't the passengers just shards of greater Entities, and hence you can't awaken a passenger's Aura without awakening that of the whole Entity? In a way, they are all one, but...well, my explanation requires both a brief biology lesson and an explanation of how I see the Entities' reproduction working.

First, consider the various types of organisms which operate in units greater than the individual organism; I'm imagining the individual shards as the individual organisms, and the Entities as the greater units. The first such organism I'll be bringing up is called the Portuguese Man of war (which is presumably a slight towards the Portuguese navy). It looks something like a buoyant jellyfish, but is in fact in a cousin taxa, more closely related to hydrozoans. Aside from its resemblance to jellyfish, the main notable attribute of the man-of-war is that it's actually a number of separate but integrates organisms (zooids), each specialized for different tasks. Some sting and paralyze prey, others catch or digest it, and so on. Despite this, most would think of it as a single organism (including, quite possibly, the man-of-war, if it could be said to have a consciousness; it certainly acts as one). Contrast with this colonial insects (I'll be focusing on termites, since they're more specialized than other well-known colonial insects). Like the zooids of a man-of-war, the individual termites are specialized for various purposes—workers, reproductive termites (usually two castes, for obvious reasons), a couple soldier-related castes. Like the man-of-war, the termites cooperate much like one complex organism, but they act independently more than the man-of-war, and most would consider them many separate organisms (again, likely including unusually intelligent termites).

I imagine that entities travelling through space, looking for a new world, are much like Portuguese men-of-war; their shards are all connected and work together; they're essentially one entity, and if someone awakened its Aura, all shards which broke off would have awakened Aura as well. Once they arrive, they break off most of these "zooids" break off, separate as worker or soldier termites; awakening any of these shards' Auras awakens the Aura of that particular shard, and probably ones which bud off, but not any others. When the cycle is complete, all of the shards on the planet gather and are split off into a bunch of new Entities or Entity pairs (probably including the cores of the original ones, surrounded with new shards) as they are sent flying into space; Entities with awakened-Aura shards might be able to awaken their own Auras, which would doubtless transform future cycles.

(It probably bears noting that Word of God states that "shards" aren't really the quanta of Entities any more than, say, grams are the quanta of steel; many passengers can be considered multiple shards put together or one split, and they all work much the same regardless. So, each of the individual "termites" is a "man-of-war".)

Anyways, to wrap this up, let's consider Aura and Changers (or Shifters). These parahumans have powers which change their physical form; I've noted that my Aura headcanon involves the defense it provides essentially working by making the user resistant to changes. How does Aura affect these parahumans? It depends. Aura tries to make you closer to your self-image; a cape who revels in his/her transformed state might find it easier to change into and stay in the other form, while one who considers said state to be someone else would find it harder. It has a bit to do with how well the passenger and the host "get along," and a lot to do with the changes involved.