"Once a Handmaiden..." is the eighteenth episode of Rapunzel's Tangled Adventure of season three. It aired on February 23, 2020, and it is the sixty-fifth episode of the series overall.
Eugene and Varian create a new weapon they call "Project Obsidian", a bazooka that shoots weaponized amber crystals to combat an impending attack from Cassandra, which the Princess reluctantly authorizes as a last resort. Meanwhile, Cassandra discovers the missing shard from the mirror and realizes the Enchanted Girl's manipulation, who she finally discovers to be Zhan Tiri.
She disguises herself in the Shapeshifting Cloak and takes on the form of a handmaiden named Faith in an effort to make amends with Princess Rapunzel. After performing in a play with Princess Rapunzel (which details their battle), Zhan Tiri strips Cassandra of her cloak, revealing herself to the kingdom and causing the guards to attack. As Eugene and Varian stand down, Zhan Tiri sneaks up and activates Project Obsidian, firing a blast of amber at Cassandra. Saddened that Cassandra would believe Zhan Tiri, of all people, over her, Princess Rapunzel falls unconsciousness due the potion that was given to Cassandra earlier by the ancient, evil sorceress. Repeating the very words of her own mother ("You want me to be the bad guy? Fine. Now I'm the bad guy"), a furious and further Moonstone-empowered Cassandra has possessed members of the Dark Kingdom's Brotherhood- Hector and Adira- unleashes the full deathly and destructive power of the Moonstone and declares Corona to be hers.
Eugene orders a fall back, and he tells Maximus and Pascal to take an unconscious Princess Rapunzel away from the fallen kingdom. Later that night, Princess Rapunzel wakes up and, to her horror, sees Corona completely taken over by the moon rocks per Cassandra's will, who sits upon the throne as its conqueror, ergo fulfilling Princess Rapunzel's greatest fear.
- Kiera and Catalina
- Fidella (and one of gopher's impersonations)
- King Edmund
- Lance Strongbow
- Stalyan (mentioned)
- Mrs. Crowley
- Quirin (cameo)
- King Frederic
- Queen Arianna
- Pete and Stan
- Gothel (flashback via hand-mirror)
- Vigor (one of gopher's impersonations)
- Little Big Guy (one of gopher's impersonations)
- Corona Village
- Cassandra's Stronghold
- Corona Castle
- Old Corona
- The Throne Room
- Snuggly Duckling
- Kingdom of Vardaros (mentioned)
- Spire Vault (mentioned)
Objects of Supreme Power
- Shapeshifting Cloak (last appearance and use)
- Cassandra's Armor
- Moondrop Stone
- Shadow Blade
- Black Rock Spikes
- Magic Blonde Hair
- Mind Trap
- Gothel's Mirror Diary (referenced by her daughter Cassandra)
- Eugene's Sword
- Project Obsidian (first and last appearance; destroyed)
- Cassandra: "Do you wanna explain to me how this got here? Back at Gothel's, I thought Rapunzel was hiding the one memory that proved my mother loved me."
- Zhan Tiri: "And?"
- Cassandra: "And you manipulated that memory, didn't you!? You took this piece out! You tricked me into abandoning Rapunzel."
- Zhan Tiri: "Perhaps or perhaps I simply pushed you to become what you were always meant to be."
- Cassandra: "Who are you? AH!! You're...you're that ancient demon, Zhan Tiri!!?"
- Zhan Tiri: "Oh, quit pretending your horrified. We're not so different you and I. We were both cheated out of destiny!! In fact, we're more like sisters than you and Rapunzel ever were!! We even want the same thing. And we can get it, if you continue to let me help you."
- Cassandra: "No, no!! I'm nothing like you. Just because I'm pursuing my destiny doesn't make me a bad person."
- Zhan Tiri: "Doesn't it? Run, Cassandra!! But you can't run away from who you are!!"
- Cassandra: "Project Obsidian, huh? Zhan Tiri was right."
- Princess Rapunzel: "Cassandra!!"
- Cassandra: "You want me to be the bad guy? Fine! Now I'm the bad guy."
- Like the season two episode title "Happiness Is..." the episode title is also a partial popular quote Project Obsidian disappeared but is replaced with a different one when Varian is shown to be wearing his outfit, apron, gloves and shoes from season one and at the near end of Rapunzel's Return while he is sitting on Fidella before a guard comes to tell Eugene that Cassandra is inside Corona to attack Rapunzel. Also, when Varian is on Fidella waiting for a guard alongside Eugene and Maximus, Fidella's saddle doesn't have a sun symbol.
- Even though Varian says that he doesn't want to hurt Cassandra during the episode, but during the episode Secret of the Sun Drop, he did hurt Cassandra and Queen Arianna after he grabbed his former crush and Rapunzel's mom with the giant robot hands because he wanted Rapunzel feel the same amount of pain and agony that he has.