- ...is actually completely useless.
- ...has some kind of weapon in it. So that Venus can carry on the good fight without him.
- ...is Sealed Evil in a Can, and Mars needs Venus to destroy it if he isn't there to stop it from breaking loose.
- ...has a MacGuffin in it that needs to be kept safe.
- ...has a memento Mars wants Venus to look after for him inside of it.
- ...really is full of confetti.
- ...is full of donuts.
- ...has a living being in it.
- ...was intended for use against Sun but will end up being used to fight Black Hole.
- ...was intended for use against Black Hole but will end up being used to fight Sun.
- ...is a Soul Jar.
- ...is an Artifact of Doom that Mars doesn't want left lying around without him to keep an eye on it.
- ...is just an ordinary moon, and it's a customary Due to the Dead to break a planet's moon when they die.
- ...contains a letter either explaining a plan of action for what to do now that he's dead, or whatever horrible secret he accidentally uncovered at some point in his life.
- ...is rigged to explode.
- ...has a Dark Secret that Mars doesn't want anyone to know.
Planets are perfectly happy to reach out and grab rocks to eat, but stars either can only digest living beings (or possibly only planets), or can only get nutrition from them.
Otherwise Sun wouldn't be so hesitant to even talk about what's wrong with him, he'd just eat moons or asteroids like Jupiter does.
- Or maybe stars can eat moons, but they aren't big enough to make a difference in how hungry they are- it might just be that planets/dwarf planets being much larger than moons is what makes the difference and that's why Sun thought of them.
He's getting bigger, giving off more heat, and sees through a Red Filter of Doom as a visual clue.
Plus, Word of God is that the planets in Nebula are older than the real ones- if Sun is older too, it'd make sense why he'd be turning into a red giant (which happens near the end of a star's life).
- Alternatively, he's turning into a black hole- with Ceres getting killed off, we know we aren't being strictly bound by factual astronomy, and him turning a black hole would hit hard with what we know about Black Hole (namely, that she's a horrifying Humanoid Abomination).
Seeing how huge it is and deciding that it'd be the jewel of their stolen-moon collection, Uranus'll decide to take it.
Mars will protest and try to stop them, and in the scuffle the moon will get broken, revealing whatever's inside.
Saturn was right!
Mars already talked to Venus about what to do if he died; that isn't a Chekhov's Gun that they're going to leave on the mantle, and Sun wasn't exactly on good terms with him last time they talked.
Plus, we don't know what state everyone's in after Ceres attacked; after he's killed once (even if it was for the right reasons), who's to say Sun hasn't gotten a thirst for blood, or that he is composed enough not to lash out if Mars continues the argument they had earlier?
She's the only one we didn't see suffering while Ceres did whatever they did- in fact, we only see her after it's over, where she seems more confused than anything else.
Black Hole deliberately had Ceres spare her, either to not set back attempts to get Earth to join her, or to try and turn the other planets against her and weaken the solar system with infighting.
- Maybe they did do something to her, but it wasn't immediately obvious: turning her into a Manchurian Agent or something.
Or at the very least he knows she exists.
That's why he's so insistent that no one goes out too far- he knows what she'll do to anyone who gets too close. What he said in Nix was that "there was nothing waiting for them but a cold void", which, From a Certain Point of View (namely, that Black Hole pretty much embodies the void in both a literal and metaphorical sense), is correct.
As for why he pretty much told Mars and co. to shut up and deal with it when they were pointing out that she was watching them... Either he didn't want to believe that she'd make an aggressive move instead of waiting for someone to wander out after all this time, or he didn't trust himself to be able to continue the discussion without doing something he'd regret, and was going to just cut it off no matter what Mars was going to say.
- Confirmed in "Lux"; he most certainly knows of her and knows what she's up to, even if they haven't met in person.
Assuming Pluto makes it to Black Hole without incident, he'll presumably meet the other dwarf planets she talked about; either they'll be able to talk clearer than Ceres could, or there'll be a Translation Convention to let us understand what they're saying.
How else could she vomit up Ceres right next to the solar system (since it took barely a panel or two for Ceres to arrive there so it can't have been too far) without anyone noticing her?
It looks like Black Hole has some kind of Reality Warping powers, or can summon minions who do: either way, the planets don't have much of a chance fighting her as they are, and Sun isn't really seeming like the most reliable person to depend on.
If the planets are going to face Black Hole and survive, they're going to need something to help them, and nothing is better at saving the heroes from the threat of certain destruction than a mysterious object given on a person's deathbed.
It'll end up not only unable to accomplish whatever it's meant to do, it'll actually make things worse for whoever tries to use it.
I mean it's not like anything else has been working out well for Mars these days.
It cut to a shot of Sun's arm as Venus promised she'd break it if Mars died; while I guess it's possible it was just meant as a general warning that Sun is still Not Right, it seems like something about the moon is going to end up involving him if Venus breaks it.
- And as a possible add-on to that: maybe it won't involve Sun when it comes into play, but he instead had a hand in creating it?
She has to have some reason to want to lure dwarf planets out to her: maybe when she consumes someone, their strength is added to hers and she can control their bodies.
The only reason she focuses on dwarf planets is that they're usually isolated and vulnerable— the same thing would happen if she consumed a planet or star, they just don't tend to listen to her.
- Random add-on after thinking about it: maybe she doesn't have a physical body, and that's why she needed to summon Ceres to do her dirty work. If so, then maybe she needs to absorb a certain amount of mass to manifest a physical body, or she just wants more lackeys to control as avatars and Pluto just looked gullible enough to convince.
Stars (or at least Sun) are older than their planets, and by Word of God teach them to talk. Given that the stars are apparently born knowing how, it seems most likely that it's genetic, and it's probably not limited just not knowledge of language. If stars are born before planets, and at least some have no other stars around and are completely alone until the planets form (i.e., Sun), it makes sense that they're born with enough general knowledge to keep them alive until they're fully grown.
Planets, forming after a star already has, wouldn't need that kind of inborn knowledge, and instead learn it from their host star. This keeps the planets from doing things like wandering into the void without realizing it's a bad idea, and also tends to create social structures where planets are led by stars, due to the knowledge as well as the size difference.
(Well, in real life that's how black holes form.) She was a star who either died in the void, or went into it and was corrupted by it into what she is now- something not quite a star, not quite dead, and not quite part of the void.
If she and Sun ever meet, it'll be a pretty dramatic Not So Different argument to throw at him- at the very least, finding that out would throw him off balance and leave him doubting himself/fearing what he might be becoming.
- If the implications are right and she's The Assimilator, then maybe she's not a dead star, she's a Hive Mind/amalgamation of every dead star, or at least multiple ones.
The Chekhov's Gun of his moon that'll only be relevant if he dies supports him dying at some point, and the Ghostfruits announcement for the upcoming #17 showing him bandaged and looking like he's completely crumbling apart.
- Mars has Plot Armor, though, and the only people who've died so far have been new characters we weren't attached to (Ceres) or in the backstory (Virginis' planets). It seems more likely that his moon will end up broken some other way, without him needing to die for it.
- Or Mercury could die— it's been shown that he was injured in what looked like the same way Mars was during the attack, that he and Sun are close, and he isn't as major a character as Mars is. His death would function as the straw that breaks the camel's back and turns Sun against the remaining planets outright, forcing them to flee into the void and end up confronting Pluto/Black Hole.
- Looking jossed; they're all injured, but none of them seem anywhere close to dead.
Black Hole could be a changeling with a Wyld of near 10, a very high-Wlyd changeling of an opposing court and/or entitlement, or a True Fae herself. Sun has a high Wyld but low Clarity that's affecting his mental state and perceptions. The planets have relatively low Wlyd but normal Clarity, with Earth and Pluto (and possibly Saturn) having an abnormally high enough Clarity that allows them to hear Black Hole (or moons) when the others can't.
The simplest possibility is that everyone is a Telluric (what with embodying space and all), or that all planets are Earthbones or Stonebones and stars are Firehearts or Gargantuans... but this is the WMG page, so let's look at every other possible Seeming/Kith (and/or Court and Entitlement) too.
- Earth: Woodborn or Waterblood, given that she's the only one who has life and water on her surface. Maybe a Playmate.
- Dawn Court
- Mars: Antiquarian or Oracle, or just plain Earthbones; out of anyone, he definitely looks the part of an Earthbones the most.
- Winter Court or Dusk Court.
- Venus: Stonebones or Earthbones; she did take an asteroid to the face without much more than a bloody nose.
- Autumn Court
- Jupiter: Oni or Troll, depending on how much you're willing to believe his vendetta against Sun is justified.
- Summer Court or Court of the East.
- Uranus: Larcenist or Lurker (but really, probably Larcenist given that they're a natural thief and smooth-talker).
- Spring Court
- Neptune: Weisse Frau or Drudge, or maybe even Snowskin or Airtouched going by Neptune's properties in real life; she's kind of a mystery as a character.
- Autumn Court
- Saturn: Gandharva or Oracle— it really depends on how much of what they know is actually correct but isn't believed and how much is just random speculation.
- Winter Court
- Mercury: Chatelaine, probably, or some other Wizened kith given his deference to Sun. Maybe a Drudge?
- Day Court, of course.
- Sun: Gristlegrinder, Gargantuan, Fireheart, or... Weisse Frau, going from how he protected them from Ceres.
- Summer Court or Day Court.
- Pluto: Playmate, Palewraith, or Snowskin— I'm leaning towards Playmate, given his loneliness as focus of his character.
- Dawn Court or Courtless.
- Black Hole: Pretty much any Darkling kith at all is possible for her if she isn't a True Fae; in particular, Pishacha, Palewraith, Gravewight, Leechfinger or Whisperwhisp all seem fitting. Could also be a Shadowsoul or Witchtooth.
- Court of the East? Night Court? Courtless?
- Ceres: Again, most Darkling kiths in general are possible for them, and Moonborn and Palewraith in particular. Depending on what happened to them with Black Hole, they could also be a Wizened of some kind, maybe a Soldier.
- Dusk Court? Court of the North? Court of the West? Courtless? It could be anything, honestly.
It looked like it had a rock for a head, so it's probably not a young star, and all the planets in the star systems we've seen are accounted for and look nothing like it. Unless that was one of Virginis' planets and the first comic took place much earlier than we thought, it can't be any of them.
Maybe it was even Ceres, pre-Black Hole! Word of God is that Ceres didn't look the way they look now before they met her, and Ceres in real life is essentially a big asteroid; the forming-thing's head looks nearly identical to the asteriod that hits Earth later on in that comic.
- That'd imply that he's actually normal-sized, and the planets are tiny.