The path of black rocks leads Rapunzel and her companions to the Big Tree, an ancient, magical place. On their way to it, they encounter the unpredictable Hector, the last member of the Brotherhood and discover the Moonstone's uncontrollable Decay Incantation inside the tree. After traversing the interior of the tree, all of them ended up in a fight with Hector near the exit, who got pushed off by Adira and fell far down to the tree's heart. In a last resort to stop them all, he removed the spear inhibiting the dark magic, awakening it. That magic possessed him and eventually overpowered Rapunzel's companions, but was foiled by her usage of the second Incantation. This however, withered Cassandra's right arm when she touched Rapunzel in an attempt to stop the incantation, although her cries of anguish managed to achieve that. As the tree starts collapsing as a result, Adira went down to the heart with the magical spear while the Coronans escape.
- Mandy Moore as Rapunzel
- Zachary Levi as Flynn Rider
- Eden Espinosa as Cassandra
- James Monroe Iglehart as Lance Strongbow
- Jeff Ross as Hook Foot
- Paul F. Tompkins as Shorty
- Kelly Hu as Adira
- Jonathan Banks as Quirin
- Kim Coates as Hector
- Cassandra sings her first solo in this episode.
- The German version of the title in English is "The Power of the Moonstone".
- This is the fifth special, followed by Tangled: Before Ever After, "Queen for a Day", "Secret of the Sun Drop", and "Beyond the Corona Walls".
- The alternative lyrics version of "Healing Incantation" was sung by Rapunzel, and the spell activated a new magic of Rapunzel's hair.
- There is a flashback of Rapunzel when she still has her short brown hair, taking place prior to the events of Tangled: Before Ever After.
- Eugene reveals it has been 6 months since they left Corona.
- By the end of the episode, Cassandra wears a new armored outfit.
- Adira reveals the existance of the Brotherhood, including that Varian's father, Quirin is a member.
- This is the third time the closing theme "More of Me" is not featured, the previous being "Secret of the Sun Drop" and "Queen for a Day".
- During the chase scene as Eugene's half of the caravan runs off the cliff and on to Rapunzel's the chain Hector threw at it, Hector himself, and his rhino is missing.