Ruler of the Ancient Seas - Episode 9

A mermaid named Lina is pressured by her sister to produce a golden egg, a symbol of supreme bloodline, or become sacrificial fodder. Remembering a past life where her sister swapped and betrayed her, Lina is determined to succeed. She finally lays a golden egg to the clan's joy, but her sister, Serena, secretly attempts to curse it black as she did before. Her spell fails against Lina's protective bloodline lock. The episode ends with Serena horrified to see her own eggs have turned black, revealing her scheme has backfired.