Eclipstar

Eclipstar is the family ship between Star Butterfly and Eclipsa Butterfly from the Star vs. the Forces of Evil fandom.

Canon
For a long time Star only Knew Eclipsa Butterfly by her reputation as the "Queen of Darkness" who wrote the forbitten chapter and ran away to be with her monster lover, a bit like how Star has written her how spells and had an off and on relationship with the half-demon Tom Lucitor. Star comes across Eclipsa's tapestry within Glossaryk's magical realm and after Star reads the texts on it she smiles as Star calls Eclipsa a "bad girl" in a good way. Due to the contract Queen Moon formed with Eclipsa as a teenager, Star's actions in disintegrating Toffee before he gets crushed by a pillar leads to Eclipsa escaping from her crystal prison. Star wasn't aware of this until the events of "Stranger Danger".

When Star met Eclipsa for the first time in the castle's garden and the way she helps with Glossaryk before they continue to have a friendly chat, she views Eclipsa as a nice lady and didn't like the way that the Magic High Commission were trying to make Star think that Eclipsa is evil. Despite Moon being on their side, Star convinces her and the commission to give Eclipsa a fair trial, as well as a nicer place for her to stay that isn't a prison cell in the castle's dungeon. This gets Eclipsa to recommend her old tower and when Star went to see her there, the state of it make Star think that the commission were still mistreating Eclipsa until the former queen shows Star the beauty view of the garden and its roses. The continue to bond during the led up to the trail, as Eclipsa gives Star advice on Marco and being someone that Star can turn to when she was having dream problems, along with Eclipsa revealing the secret tunnel and passage ways in the castle that she uses to stretch her legs without the guards knowing, but trusts Star enough to share that said secret. During the party Star hosts at the castle Eclipsa once lived in with her monster lover and child, as Star tries to bring people and monsters together, she learns that her former St. Olga's Reform School for Wayward Princesses headmistress, Miss Heinous is Eclipsa's Mewman/monster hybrid daughter, Meteora Butterfly. Star was shocked by this and Mina Loveberry prevented her from asking Miss Heinous/Meteora questions about her being a Butterfly, so she turns to her mother who later goes to see Eclipsa on the subject and learns that she has never heard of Star's ancestor Festivia Butterfly. Who was recorded to be Eclipsa's daughter in the official Butterfly family records instead of Meteora.

Before Eclipsa's trail began, she, Star and Moon came up with the plan to get the truth out of the Magic High Commission. During the trail as the Commission mark Eclipsa's answers as "evil", Star disagrees with their choice as she finds the love Eclipsa has with Globgor to be romantic and she has hurt any babies. After the Box of Truth tries to crush all of them, Star tells the commission that them keeping their secret making them no different from the villain they have cast Eclipsa as, and it gets Rhombulus to admit that they had swapped Eclipsa's hybrid child with a peasant girl to continue the Butterfly family, while lying to the family that Star and Moon are part of. Star was sad to learn that she and Eclipsa weren't never related by blood and how her family have been fouls royals all this time, before Star dashes off she frees Eclipsa from her shackle cuffs.

After Eclipsa's real daughter learns the truth and plans to punish Star and her family for taking the throne away from her, Eclipsa tries to stop Meteora from doing so but ends up causing Moon to disappear and later informs Star what happened to Moon and the danger that is coming her way. This makes Star the new acting queen while Eclipsa is arrested for defending Meteora from Moon. In the events of "Conquer", Eclipsa escapes her chains to aid Star by taking on Meteora with her dark magic. Once Meteora was defeated and believed to be dead, Star felt sorry for the tough choice Eclipsa was forced to make on her behalf and as Eclipsa gives the Royal Magic Wand of the Butterfly family back to Star, the young acting queen decides to right the wrong her family has done to Eclipsa by telling her to keep the wand. Shorlty after they learn that Meteora is alive and has been reverted back into a baby, Eclipsa thanks Star before she takes off with her child.

Star's actions has Eclipsa reclaiming her role as the queen of Mewni who went back to live in Monster Temple and during Star's search for her mother, Eclipsa offers her a room at the temple turned castle. After Star does find Moon, she continued to stay with Eclipsa as she felt an obligated to help Eclipsa with her queen duties from being the now former princess. Along with the fact that not everyone is happy with the idea of Eclipsa being their new queen, due to Eclipsa's past, fondness for monster and reputation. Star understands how much Eclipsa loves Globgor and wants to free him from the crystal, but she convinces Eclipsa not to in fear of the danger Globgor might unleash upon Mewni. Eclipsa understand that Star means well, but it hasn't stopped her from looking into Star's mind for the location of the surviving part of the Book of Magic.

Fanon
Because the series first had Eclipsa as one of Star's relatives, fans saw Eclipstar as a canon family ship until "Butterfly Trap" reveals that they aren't related at all, but it doesn't change the fact that there were a few family-like moments between them and Star herself isn't so different from Eclipsa. They have created their own spells and well in love with monster-like people. There have also been a few fans who prefer to femslash ship them together, despite the age gap between them and the lie that made them think that they were related by blood.

On AO3, the ship has seven gen fanfics and only two romantic fanfics, while Fanfiction.net has 65 and most of them features the two sharing a family bond with one another beside Star's friends and her mother.

Fandom
FANFICTION
 * Star/Eclipsa tag on FanFiction.Net
 * Star/Eclipsa tag on FanFiction.Net
 * Star/Eclipsa tag on FanFiction.Net

WIKI

Trivia

 * In the season three opening, Star and Marco pass the crystal that Eclipsa is sealed in.