In Season 3, Bella Hartley moved to the coast when Emma Gilbert left to go travel the world with her family. In the previous seasons, the three mermaids: Cleo, Emma and Rikki wore lockets to help them remember how special they were. After Emma left, the new trio replaced the lockets with jewel pendants, with stones found inside the rocks of the walls of the Moon Pool. When in contact with each other, these crystals generate immense energy to cause power outages of a city, and a blue light that mesmerizes the girls in the same way as the full moon.
- These stones might be the same as the stones found in Moon Rings, as they both appear to hold moonlight and can simulate the effects of a full moon.
- As of Mako: Island of Secrets, Rikki no longer wears her crystal necklace, possibly due to her disconnecting with both Cleo and Bella.