She-ra and the princesses of power, book 3: Song of the Sea Witch
Tracey West2019

When a friend is in danger, She-Ra is ready to fight.
Just after the most recent Rebellion victory, a messenger from Salineas arrives in Bright Moon. He says he's there on behalf of someone named Queen Calypsa. But Salineas is Mermista's kingdom! What happened to her?
The messenger won't say, but Adora, Glimmer, and Bow are determined to find out. And when they arrive in Salineas, they find it in the clutches of an evil sorceress-with the Horde on the way. Can She-Ra defeat Calpysa and save Mermista before it's too late?

Titre original : She-ra and the princesses of power, book 3: Song of the Sea Witch (2019)