I mean proper Outsiders, from outside the narrow banks of time and space. Things that have slipped in when no one was looking. Things that don't make sense, or at least not any sense that we can comprehend. They are disruptive to the setting--they spoil it. They ruin the logic of it. They expose inconsistencies. If it were a TV show, they would break the fourth wall, or spoil the ending of the series for everyone.
Anyway, this post has 4 points to make. The first two have already been established (or at least strongly alluded to) while the last couple are novel.
This is not canon. (There is no canon.) But the existence of Outsiders seems to imply a few things.
1. The things outside our own universe are much, much bigger in every way: time, space, and significance.
Our universe stretches from big bang to its inevitable heat death, spans a few billion years. The time scale outside that extends for trillions or quadrillions (depending on how you count the cyclic parts).
We cannot escape the walls of our universe, because there are no walls. It wraps back in on itself. To escape this universe would require more energy than the universe contains.
To continue a previous analogy, we are bacteria in a Petri dish. The greatest bacterial heroes cannot see past the walls of their home, and our greatest works will not survive the experiment.
2. Human souls have a history prior to their conception. It is much longer and much more important than everything that happens after conception.
Before you were plugged into your mother's endometrium, you were someone else. Someone with a full life, with triumphs, failures, friends, and enemies. Because that life occurred on the extracosmic scale (see above) it is too large to fit in our brains, and what little we remember is too complex to be understood.
This life is a reduction of what we once were. It's stuffing the soul of a human into an ant, or perhaps an amoeba. What is retained? What can an ant-brain know of its previous life?
That is why the Awakened are so furious to see us clinging to our ant-lives. Looking at us, they can see the creatures we were, before we were reduced to simpering idiocy by the machinations of cruel sperm and scheming egg.
A trillion-year friend reduced to a simpering, traitorous idiot in only a few decades. (Less than an eyeblink, for some.)
And while our life here is short, the universe traps our souls for far longer. And while we are here, we are not out there, where there are much more important things to do. It represents a neglect of duty, as if we were emperors who refuse to stop playing tea party with stuffed animals while the kingdom burns down around them.
No matter how important our troubles seem, or how important our achievements, they are utterly dwarfed by the greater multiverse. Centerran wars leave hundreds of thousands dead in the mud. Wars in the multiverse leave quintillions of souls banished to the coldness between the stars.
(Fractals are a theme in Centerra. If you zoomed in on a grain of sand, you would find tiny kingdoms of dust mephits fighting and dying amid the milliseconds, vying for control of a square micron in multigenerational wars that last entire seconds.)
Anyway, there is a third business to this business, one that involves the multiverse.
Or to put it another way: whenever a coin is flipped, it creates two universes: one where the coin comes up heads, and one where it comes down tails. (Don't tell me that a coin is too big to be influenced by quantum events. I don't want to hear it.)
A lot of coins are being flipped all the time. A lot of coins. Every nanosecond, a billion universes are branching off from our own. (And our own universe isn't special. It's just another branch like all the others.) And another nanosecond after that, each of those billion universes spawns off another billion universes.
Whenever you roll a d6 and get a 6, you create five more universes, one for each other result.
Whenever your mother dies of the plague when you are five, somewhere there are a billion billion other mothers that lived to happy old age.
Whenever your father sits back in his chair and licks his thumb before carefully turning the page of his hymnal, there are a billion billion other fathers who are burning alive, caught in the fire that started after they dozed off and dropped the pipe on the carpet.
Everything that is possible has already happened.
This is because a great deal of unlikely things are possible all the time. How many chances do you have every day for a once-in-a-million experience? (A lot.) They don't happen to most of you, but they certainly happen to at least one of you. And that lucky one goes on to spawn their own nested set of a billion billion universes.
This is a lot of mass and energy, but its not infinite. And of course, the parallel universes don't interact.
Unless you are an Outsider.
4. Outsiders span the parallel dimensions. For the most part, they can't move anything between universes except knowledge.
Each Outsider is dimly aware of all of its local parallel selves--those who are separated by only a recent branch in the timeline. It's a fuzzy, ever-changing qualification, but it works.
So when an Outsider enters combat and makes an attack roll that has a 75% chance of hitting, they can see 15 slightly different universes where the attack hit, and 5 universes where the attack missed. One of those universes is their own, while the other 19 are their local neighbor-selves. And each of those universes will have it's own branches (for different results of the damage die, for example).
This awareness gives them a different sense of perspective than us. Since they spread across a billion universes, fighting a billion (non-unified) foes, they don't mind losing a few battles in order to win the war.
They don't think like we do, in terms of life and death, winning and losing. They think in terms of percentages. This fight is 94% victorious. That poisoned killed 25% of me. I devoured 99.9% of her bodies.
It is very hard to die permanently in the multiverse, since if it is at all possible for you to be alive, you will be alive somewhere. The only cost is influence (more on that later).
In combat, an Outsider might stand perfectly still and allow you to hit it. It is learning how hard you can hit, and how much damage you can do. It will use this information to triumph against you in a billion other worlds.
In combat, an Outsider might flee even though it seems to be winning. It needs to scout out another room so that all of its billion twins can use that information in their universes. It's already pulled your brains out of your sinuses in a billion universes; it can afford to squander this one, since the other billion selves need a piece of information more than they need one more negligible victory.
In combat, an Outsider might hurl itself at you, nearly suicidal. Again, it is not trying to defeat it, merely learn from you, so that all of its other selves can triumph in their respective universes.
And when you talk to an Outsider, be assured that each of the billion Outsiders is asking you a different question.
One will ask you what your name is. Once you answer, they will all know.
Simultaneously, in a different universe, another Outsider will ask another you where you are from. Once you answer, they will all know.
Simultaneously, in a different universe, another Outsider will ask another you what you are doing here. Once you answer, they will all know.
That's three questions. There are still 9,999,997 other Outsiders asking questions. Is it small wonder that some of the questions they ask seem nonsensical or trivial?
So when the first thing they say to you is, "Lettuce or Cabbage?", rest assured that it is not a trivial question. They've already asked you all the important questions in parallel universes and gotten their answers. They're just going for completion.
Talking to an Outsider is enormously one-sided. A billion humans ask a billion questions to a billion Outsiders, but its the same question. A billion Outsiders ask a billion questions to a billion humans, and each one is different. The human learns one thing. The Outsider learns a billion (including whether you prefer lettuce or cabbage).
This is why people say that Nobodies or slaad are insane. (Slaad are the closest thing we have to "naturalized" Outsiders.) Humans see only the battle in their own house, and miss the war consuming the city.
It is not insane to allow themselves to be struck dead. They will kill a billion of you with the knowledge they gain.
It is not insane to flee from a combat that they are winning. They have already triumphed a billion times, and this will allow them to gain some small knowledge.
It is not insane to ask strange questions, like "What color was your mother's horse?" They have already asked a billion questions. (That's how they learned your mother rode a horse.)