Warning Spoilers Ahead.
With the shocking reveal that Eclipsa is not related to Star at all, which now the I look over past evidence it’s quite obvious at least when we look at the smaller details that are hidden within the series. Eclipsa’s and Metora’s eye’s are almond shaped unlike star and moons eyes who have big round eyes and who do we know in the series who has almond shaped eye’s, Marco Diaz. Throughout the series I have speculated quietly to my self that these two are related because of the mole placement on both of there faces but I quickly dissmised this because it didn’t make sense how could these two characters be related but then after this episode everything clicked into place so perfectly I couldn’t believe it and the amount of evidence just keeps growing and growing.
In the episode Deep Dive, Marco was able to use the wand, now I know that this isn’t very solid evidence but as we have seen with the peasant girl who was able to use the wand and Star can use the wand even though she has no relation to Eclipsa so it’s safe to say magical ability is something you are just born with and anyone can use if they the right tools. The symbols on each of the butterfly family are said to be given from being in contact with powerful magic for so long, which explains why the females only seem to inherit them as they do not train with magic which explains Festivas marks as she had been around the wand since she was just a baby but she didn’t get them right away as we are shown by the council and I should mention that when crab monster gets the wand he doesn’t get the marks either and before you shout monster, Metora is half monster and has the marks. When Marco uses the wand he got red crescent moons on his cheeks which by all accounts is a little weird, when Ludo was wielding half of the wands power he should have technically have some sort of symbols appear on his face even if they were just barely visible because while still half of the wands power as we have shown half is still extremely powerful as the full extent of the wands powers has yet to be fully explored in this universe, what we know is that the wand is a powerful magical object that we know little about it despite it being shown constantly through out the show. What we know for certain is that the wand can corrupt an individual, monster’s seem the most susceptible to this as when the humans or mewni’s wield it they are usually fine as I have not seen evidence to the contrary and that with each new wielder it changes with the user and it reveals what is inside of a person to the outside world as we have seen with Marco when he got the wand.
When Marco’s uses Stars wand it transforms and it takes a rather monsters form. In the original concept art for his transformation sequence you can see the design was rather monstrous and I honestly thought this was strange from the way Marco acts in general but we have to remember that when Marco read from Eclipsa’s chapter he became possessed, he is easily suspetipal to dark magic turning him into a completely different person as we see in the hand episode. When Star goes to fix Marco’s broken hand she accidently turn’s it monstrous, at first he’s disgusted by it but then after he beats up someone by accident he quickly becomes seduced by it’s strength sort of like a former Queen we know getting seduced by the big bad monster.
So where does Marco fall into the equation of his relation to Metora as we know she is about 300 years old give or take a few months, well I think he’s her grandson yeah I know seems a little strange though it does follow the celestial naming process as Marco derives from the ancient Latin god Mars so it would go from Eclipse, Metor, Mars. Although I do not know which one of Marco’s parent’s would be Metora’s daughter the only person I could correctly guess would be Angie because of her almond eyes and although her name does not appear in the equation it could be that her name was changed at some point.
Now addressing the lack of monstrous appearance could either be one of two possible options for him. From Metora’s appearance it seems that the human side of her is dominant rather the monster part, so if she copulated with a human then the domiant side of his genetics would have taken over or when he get’s the tentacle arm before it disappears it tells him that will always be apart of him meaning he is hidden under a glamour, sort of like how Metora was for such a long time and that’s his real arm again monster family do seem to pass down genes the way humans do as we have seen from Ludo but as that is the only family as they are the only monster family I have seen in the series and Buff Frog does not count as him children were adopted so there is a little wriggle room here because for all we know there genetics could operate on fishman island rules (one Piece) where children can look nothing like there parents.
Everything has been written to set up that Marco is in fact Metora’s grandson and with this premise there is a possibility that Marco is in fact next in line for the throne and before you get your panites all in a twist telling me that boys cannot inherit the throne of Mewni I would like to point out that he is in fact a honorary princess so he could inherit the wand and if I am being honest here Marco would make a far better ruler than Star or Moon. He has a mindset so different from everyone else in the kingdom. Star wants to end the bigotry to monsters but she can’t as she can’t really comphrend what they have gone through. Marco can do this, while there aren’t any monsters on earth or they don’t appear as such. With him being a minority he’s able to understand what it’s like to be judged on appearance but it’s more then that, he’s diplomatic, but he also see’s the value in individuality he wants to help people, but understands the bigger picture in prioritizing to achieve the most good. This boy I predict will be the future Queen of Mewni and he will be freaking bad ass.