Moonclipsa

Moonslipsa is the femslash ship between Moon Butterfly and Eclipsa Butterfly from the Star vs. the Forces of Evil fandom.

Canon
When a teenage Moon was made the new Queen of Mewni after her mother was killed by Toffee and needed to come up with away to stop him, Glossaryk recommends the Evil Chapter that was written by Eclipsa before she was sealed away. This inspires Moon to ask Rhombulus to allow her to speak with Eclipsa what the spell she'll need to stop Toffee's heal ability, despite knowing that Eclipsa is known as the Queen of Darkness and wasn't fully sure if she can trust her. Once the top part of Eclipsa was freed her crystal prison and asked Moon to give her a candy bar to regain her strength, Eclipsa notices that Moon is holding the Royal Magic Wand of the Butterfly family and was surprised to see it being passed to someone so young. Until she realizes that Moon has lost her mother and begins to sympathy with her as she too had lost hers when she was younger than Moon. After Moon asks Eclipsa to give her the spell she needs to kill an immortal, Eclipsa agrees to do so if Moon forms a magical contract that will allow Eclipsa to escape her prison once Moon's target is killed. Even though Moon does form the contract with Eclipsa and uses the spell when she faces Toffee, the young queen only injures Toffee in order to keep Eclipsa in her crystal, as well as the fact that the uses of Eclipsa's spell has strained Moon's hands with its darkness like Eclipsa's are and now wears gloves to cover them up.

Over the years Moon kept her encounter with Eclipsa a secret and when Star started to show signs of having similar traits that Eclipsa has Moon becomes worried. After Moon was made to believe that Star was dead, she forgets about the results of her contract with Eclipsa as she uses her dark spell again. Once Toffee was defeated Moon knew that the contract has been completed and immediately makes her way to Eclipsa's crystal to see if her past actions have indeed freed one of Mewni's past criminals, once Moon sees that Eclipsa was still trapped within her crystal like the way she left her all those years ago she felt relieved. When the current Queen walks from the past queen, however Eclipsa's crystal prison begins to crack. By the time Moon finds the freed Eclipsa she has already gained Star's trust, and despite Moon wanting Eclipsa to be resealed as she tries to warn Star about the danger that Eclipsa and her dark magic will bring upon to Mewni she agrees to prepare a trail to decide Eclipsa's fate, by looking over her past crimes and see if she deserves a second chance or not.

After Star informs Moon about Miss Heinous being Eclipsa's Mewman/monster hybrid daughter, Meteora Butterfly while their family records state that Eclipsa's daughter was named Festivia, the Queen goes to see a skeleton guitar playing Eclipsa to confirm Star's clam that was proven to be true. This gets Eclipsa to convince Moon to take a quick look at the original guarded records to see if they can learn what happened to Meteora, Moon wasn't happy about the idea or the fact that Eclipsa surjects that they think of it as a "girls night" as the queen sneaks Eclipsa out of her tower. Eclipsa serves as Moon's guide during their time searching the royal archive in the Bureaucracy of Magic. Even though they didn't get the answers they were looking for from Eclipsa's scroll being altered to cover something up, Moon can see that Eclipsa was sad about her missing daughter and decides to inform Eclipsa that Meteora may still be alive after three hundred years. This surprises Eclipsa before Star's arrivals gets the three to form a plan to get the truth from the Magical High Commission at Eclipsa's trail. Moon and Eclipsa keep up appearances during the first part of the trail to hide the trap they set and after Moon and the Commission ask Eclipsa their questions the Queen allows Eclipsa to ask one of her own, so they can uncover what the Commission is hiding from them. It turns out that Moon and Eclipsa were never related to begin with due to the Magical High Commission switching Eclipsa's hybrid daughter with a peasant girl to ensure that the power of magic wasn't passed down to a monster, while Festivia continues the "replacement" Butterfly family line that Moon is apart of.

During Moon and Eclipsa's search for Meteora they learn that she is planning to punish Moon's family for taking Mewni's throne from them, while Eclipsa holds no sill will towards them and tries to convince Meteora to abandon her quest while Moon's queen duties has her fighting Meteora the moment Eclipsa's peaceful attempt failed. Eclipsa's mother instances, however, has her stopping Moon from hurting her daughter while Meteora uses her mother's actions to sap up half of Moon's soul. Eclipsa then watches Moon retreat through a portal to the Realm of Magic, where its magic causes Moon's memories to be wiped from her mind. As for Eclipsa she felt guilty for what happened to Moon and after Meteora was defeated Star allows Eclipsa to keep the wand. Moon's absence and Eclipsa being a past Queen of Mewni who has gained back her wand has her resuming her original role. After Moon was found by her family and was later taken to Eclipsa's Monster Temple turn castle, Eclipsa tries to bond with Moon as the later's lost memories as her getting to know Eclipsa all over again. Even though it looked like they were bonding a part of Moon felt that she can't trust Eclipsa and helps to form a small village for people who aren't happy with Eclipsa's rain. When Moon's memories start to return and Mina takes advantage of her to get rid of Eclipsa, Moon tries to secretly remove Eclipsa from the throne. By having Eclipsa's monster husband freed to give Eclipsa a bad image at her coronation, but it back fires and Moon acted like she doesn't mind that the people are now excepting Eclipsa and her monster family to keep suspicion away from her, and even though Eclipsa has already figured out Moon's role in it she chose to not say anything. Since Moon's actions has allowed Eclipsa to be with her true love again and she is grateful for it.

Fanon
After "Total Eclipsa the Moon" aired, Moonclipsa gained a decent size following and even though the series had first featured Eclipsa as one of Moon's many ancestors, fans preferred to ship them romantically than to have Moonclipsa as family ship long before "Butterfly Trap" reveals that the two were never related to begin with. There is also the fact that season three had Moon and Eclipsa form a trusting bond during the lead up to the trail, while season four has Moon being weary of Eclipsa before Mina convinces Moon to rise up against Eclipsa.

On AO3, the ship has eight fanfics, while Fanfiction.net has 25. Along with Moonslipsa having a decent size fanbase on Tumblr. Some of its fanart and fics depict Moon as her teen self to reference the day the two met as one queen to another.

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

TUMBLR

WIKI

Trivia

 * Both Moon and Eclipsa had lost their mothers at a young age.