Grants merpeople legs
Reversing the spell of legs
Putting people in a coma
Light of the Full Moon
Drains without moonlight
Can be drained by the Trident Stone
The Moon Rings are mermaid tail-shaped rings with a blue moonstone embedded in the middle. It is a powerful object, and may be used for perform powerful and complex magic. At some point in time, the first mermaids saw the power and strength of the blue moonstone and created a ring (talisman) for the other mermaids as a means to help them channel and direct their power more efficiently.
The Moon Rings store moonlight and only works in a place that can receive full moonlight, such Lyla used it to open the Trident Cave, but it did not work inside. When a mermaid graduates Mermaid School, she is given a Moon Ring and is initiated in their respective pod. If a mermaid loses her Moon Ring, it will be near impossible to receive a new one unless they can prove to their respective Mermaid Council their worth.
The Moon Rings accompany the mermaids' transformation, i.e. if they take a human form, the Moon Ring will remain in place and vice versa. In Moon Ring 2 it is shown that the rings' stones react to mermaid magic. Twice, the mermaid trio's use of magic in close proximity to the ring caused its stone to glow and release a beam which stunned Rita. However, the properties of a moon stone can be altered, like the trident's which was altered to absorb a mermaid's energy rather than react to it.
It is implied that the Moon Rings need to be placed in shells to function. Improper use of powers or less powers than required is also implied to cause problems, as seen when Lyla and Sirena attempted to stop a rainstorm using the Moon Ring without Nixie, causing snowfall indoors. The rings' source of power is placed within the moonstones. Moon Rings also depletes over time, and to load them, they have to be exposed to the light of the Full Moon, or another object that stores full moonlight, such as the Trident.
Moon Rings are a merperson's powers, but magnified a thousand times. Moon Rings are dangerous and if a mermaid doesn't know what they're doing or if a land person goes outside during a Full Moon, it can be harmful to themselves or others. To use a Moon Ring, a mermaid has to focus on their intent. A mermaid has to also focus their energy on the Moon Ring and meld their thoughts with it. A mermaid has to also be positive and unleash positive energy when using a Moon Ring. A mermaid has to also focus their mind on what they want the Moon Ring to do.
- Rita Santos (she gave it to Lyla)
- Sirena (from Aquata)
- Nixie (the one Zac found in the ocean)
- Lyla (Rita's moon ring)
- Aquata (got a second one)
- Mermaid Pod members (majority)
- Unnamed Mermaid (formerly, Zac found her ring in the ocean)
- Evie McLaren (formerly, she gave hers back after losing her tail)
- Legs Spell - Mermaids can perform a spell to grow legs, but that kind of magic is possible only on Full Moon. As the Moon Rings store the light of the Full Moon, the mermaid who has this ring, need not wait until the full moon to grow legs. The legs are equal to that of humans who have been turned into mermaids by magic: while dry they have legs, but as soon as the water hits them they grow tails. It's not known if this spell is reversible, but most likely is.
- Rain Stopping Spell - Mermaids can cast a spell to hold back the rain.
- Snow Falling Spell - Mermaids can cast a spell to make it start snowing.
- Hydro-Thermokinesis - Mermaids can cast a spell to melt ice and snow.
- Opening the Trident Cave and the Merman Chamber - Moon Rings have the ability to open the land entrance to the Trident Cave and Merman Chamber on Mako Island.
- Coma - They also seem to have the ability to put people into a type of coma as seen in "Moon Ring 2" when the girls were trying to get the moon ring from Zac, they accidentally used their powers on the moon ring and the blast hit Rita, knocking her unconscious.
- Chlorokinesis (Plant Manipulation) - Mermaids can cast a spell to grow/manipulate plants as Rita made the seaweed grow and this could be used to provide camouflage, and the same thing could also be used on a kelp forest as stated by Rita.
- Healing - They have the power to heal as shown when the girls (Sirena & Nixie) and Rita were able to heal Lyla after being zapped by the Trident.
- Force Field - It could be used to provide a magic shield/force field, like in "Decision Time", the girls used their Moon Rings at the same time to prevent Cam from being turned into a merman and taking over Mako.
- Enlargement Spell - Mermaids can perform a spell to enlarge an object like when Mimmi used the Moon Ring to make the crayfish bigger.
- Shrinking Spell - Mermaids can perform a spell to shrink objects. Mimmi shrunk the crayfish after making it too big and Evie accidentally shrunk herself when trying to remove the ring from her finger. Mimmi cast a Northern Shrinking Spell on a Chinese Puzzle Box to trap the Water Dragon.
- Duplication Spell - Mermaids can perform a spell to duplicate matter in number. Mimmi and Ondina performed the spell successfully.
- Sleep Spell - Mermaids can perform a spell to make someone fall asleep. Ondina performed the spell on David after he was enchanted by Sirena's song.
- Containment Spell - Mermaids can perform a spell to contain things. Weilan has a puzzle box in her apartment to contain dangerous spells and broken enchantments. Mimmi used it on a puzzle box along with a shrinking and adapting spell.
- Trapping Spell - Mermaids can perform a spell to trap a creature. Northern mermaids trap sharks in ice prisons.
- Adapting Spell - Mermaids can perform a spell of adaptation. Mimmi performed the spell along with a shrinking spell on a Chinese puzzle box.
- Incineration - Mermaids can perform a spell to incinerate objects. Mimmi and Ondina performed the spell successfully to destroy a Chinese puzzle box enchanted with shrinking and adapting spells.
- Object Manipulation - Mermaids can perform a spell to manipulate objects. Ondina performed this spell to demonstrate the moon ring's power to Evie, who then enchanted a mop to clean the floor. When the mop got stuck in the bucket, she boosted it with extra power, making it spin out of control. A mermaid can use this spell to shape objects into something else. Eastern mermaids shape clumps of seaweed into land people and make them dance on top of the water.
- Cyrokinesis - Mermaids can perform a spell to freeze objects. Mimmi performed the spell to freeze the mop. Ondina and Mimmi also freezed water into shapes of giant sea creatures, put them in front of fishermen and shattered them when they first got their Moon Rings.
- Levitation - Mermaids can perform a spell to make objects float in midair. Ondina demonstrated it to Evie, who then did the same thing, but found herself unable to undo it.
- Remote Spell - Mermaids can cast a spell to cast a spell on someone or something from a distance. Mimmi and Ondina attempted to cast a Remote Spell on the Fifty Moons Potion to try to get Evie's tail back, but it backfired.
- Accelerated Growth Spell - Mermaids can perform a spell to accelerate the growth of something.
- Hydrokinesis - Mermaids can perform a spell to control and manipulate water.
- Storm Spell - Mermaids can cast a spell to summon a powerful and strong storm full of thunder and lightning.
- The Trident and the Moon Ring, both share a Moonstone, only the one in the Trident is much bigger, thus the power of the Trident is one hundred times more powerful than the Moon Ring.
- A mermaid only gets her Moon Ring when their training is complete in Mermaid School and they are initiated into the Pod.
- It is not known what happens if a land-person is wearing the ring on a full moon, but it probably would be dangerous, as stated by the girls.
- While very similar in look and function, the Moon Ring stone is different than the Crystal Necklaces stone.