The Power of Three is a power that is possessed by the Charmed Ones, with the current holders being the Vera-Vaughn sisterhood. This is said to be the strongest kind of magic that has ever existed in this world. However, this also comes with the problem that, in most cases, the might of the Power of Three overwhelmed the Charmed Ones, and caused one of the trio to die.
After their auras were stripped, this appears to have rendered them unable to access the Power of Three as well. Mel and Maggie have developed new active witchly powers, while Macy regained an advanced form of her original witch power. However, the Power of Three remained elusive, until a chance encounter with an old Elder helped the sisters realise they could take on and regain the Power of Three.
The Power of Three is the collective power of the Charmed Ones that increases their magical strength. Their spells are more powerful, and it allows them to fight and vanquish upper-level demons and to achieve supernatural feats (such as exorcizing the Harbinger) which cannot be achieved by other witches. When they join hands and cast a spell, their hands glow.
While most of the spells written in the book require the Power of Three to take enough effect, it isn't always necessary for all three sisters to chant a spell together as long as they are all together at the same time. For example, Macy and Maggie cast the spell to invoke the Moirai while Mel was in another room with Niko.
The Power of Three requires harmony between all three sisters in order to be functional; if there is any discord between them, the Power of Three will be weakened (to the point it can even be rendered powerless, if said discord is intense enough) until the sisters resolve the issues at hand.
Throughout the Series
In 2018, Marisol Vera began the process of unbinding her daughters' powers before she was murdered. Their powers were activated three months later when all three sisters reunited at Vera Manor but they could not access the Power of Three until they accepted their destiny as witches. Once the sisters all agreed, they used the Power of Three for the first time to vanquish the demon, Taydeus.
An Imposter Demon would later take Marisol's form to trick the Charmed Ones into helping it retrieve the Prism of Souls which was contained inside a mirror. The sisters found it inside a triangular box and used the Power of Three to open the box as well as escape the mirror they were trapped inside of.
A few days later, a shapeshifter went after Mel's girlfriend, Niko Hamada, which forced Mel to alter history to protect her. She and her sisters drew the Moirai symbol together, then Macy and Maggie cast the spell, which altered events and everyone's memories but theirs.
A few weeks later, a Shadow Demon started hunting sentinels for the shards of the Scythe of Tartarus, which were being guarded by them. Realizing their mother had the last shard, the sisters lured the demon into a trap and tried to vanquish it with a spell. However, the demon summoned the last shard, which knocked down Mel and disrupted the spell. A mysterious individual intervened and stole the Scythe and the Shadow Demon left.
When the sisters fought the Queen of the Cicada Demons, they used a spell to vanquish her. However, the effect was slow as she was too powerful. Knowing her death was inevitable, she tried to self-destruct to kill everyone. However, Macy managed to kill her with a control panel.
On Christmas Eve, Hunter Caine tried to attack the sisters for wounding him. His half-brother, Parker, came to their rescue and tried to banish his brother to Tartarus. Growing weaker with every attempt, the sisters then grab the staff and cast the spell together, successfully banishing Hunter, but Harry gets accidentally sucked in in the process.
A few days later, the sisters fought Alastor Caine. He had the upper hand at first until Maggie joined hands with her sisters, and together they generated a powerful shield that held back Alastor's fire. Their combined magic proved stronger than his and started to blow his own power back at him until he teleported away.
In January 2019, the sisters used a spell to expel The Maestro from Mr. Miranda. The spell didn't work the first time because of the girls' internal conflicts. It was then revealed that the Power of Three doesn't work if the sisters are in disorder and not focused on a common goal. When the girls resolved their conflicts, they were able to fulfill the spell.
After touching a rune in the Vortex Viribus in Spring of 2019, the sisters' power expanded to the point where they were able to strip Charity Callahan of all of her powers without physically having a connection but mentally.
In April 2019, the sisters were able to produce another force-field to fend back Fiona Callahan's deathbolts, deflecting them back at her although this did not affect her because of her immortal status.In May 2019, the Power of Three was broken when Macy took on the Source, and as such, she began to feel distant and insecure of her sisters and being abandoned. Due to these feelings, Macy attempted to rectify it by using her new powers to rewrite history to make it so that their mother never died. However, each revision was never able to have Marisol alive and the Charmed Ones instigated, as Marisol's death was fated to happen for the sisters to become the Charmed Ones. As such, the Power of Three was never able to be used in Macy's alternate realities. In one of Macy's realities, in which she was never resurrected, Marisol was able to show a spell to Mel and Maggie that would take them back to when the Power of Three was first shattered so that they could attempt to repair it. It took Maggie and Mel showing Macy that they cared about her and would never leave her to repair their sisterly bond, and allowed them to all cast a spell that would extract the Source from Macy and trap it in her pendant.
Three weeks after defeating Alastor, the sisters were attacked by a powerful assassin. They tried to stop him with a Power of Three spells, but it was only strong enough to slow him down. Since their individual powers were stripped when they went through the portal to the Command Center, the Power of Three became ineffective as well.
After more than two months, when Mel and Maggie received new powers, the trio of sisters tried to restore the Power of Three and they started to succeed, but unfortunately, the recovery was interrupted since Macy was not able to receive her witch powers by that time. Distraught, Macy gets Abigael's help in removing her demonic powers, in hopes that this would help restore the Power of Three.
While digging through the floor in the Command Center, the sisters accidentally trigger a security system that locked them inside and rendered their powers useless. Hoping to turn off the system, the sisters all touched the Book of Elders at the same time, accidentally conjuring a name list on all the previous Charmed Ones. They realize there had been other Charmed Ones in the past and questioned the Guardian who looked over the system. The Guardian then trapped them inside a cage of deadly laser beams, prompting them to admit their innermost secrets. By admitting them, the security protocol was negated and a new path was opened. The Guardian presented herself as one of the previous Charmed Ones and warned them about the Power of Three's danger in hopes that one day a sisterhood would be powerful enough to break the cycle. After spending some time to think about it, Macy decided to restore her power and try to break the cycle of the Charmed Ones, to the joy of Mel and Maggie.
When the Charmed Ones rescued a witch from a zealot in the Faction, they discovered she was in fact an Elder. Celeste's research into transferring magic had fallen into the Faction's hands, and Celeste explained that the only way to stop them was to use the Power of Three. Mel, Maggie, and Macy had to explain how they were stripped of their powers when they came through the portal to the Command Center, but Celeste knew a way to help them regain the Power of Three and started chanting a spell to induce sleep, despite the sisters' attempts to stop her. Macy's dream was a reality where Harry and Abigael had married and had children, while Mel and Maggie reformed the Power of Three with Abigael; Maggie's dream was where everyone saw her as a child, and no one took her seriously over a demon attack; Mel's dream was one where she was trapped in an asylum.
In Macy and Maggie's dream, one of the sisters died; Macy, when attacking Abigael, accidentally stabbed Maggie in the heart, while Maggie's dream had Mel be attacked by a magic-infused corpse and die as a result.
Celeste reasoned to Harry, when he questioned her motives, that she was not trying to harm the sisters, but help them realise their fears, but made a miscalculation: the sisters' greatest fears were losing each other, not dying themselves. Harry demanded to be let into their dreams to help them wake up, and successfully did so.
Now awake, the Charmed Ones once again tackled the magical corpse but realising they need the Power of Three, agreed to take it back despite the risk, and their mutual bond finally restores their magical bond and using it to destroy the corpse. 
When Vivienne broke into the Command Center and poisoned the black amber tree, she went after the Charmed Ones to destroy them. The Charmed Ones then used the Power of Three against her. As the prism glove siphoned their powers, it soon proved too much and soon exploded, killing Vivienne in the process.
- Unlike the original series, the Veras had a choice as to whether or not they became the Charmed Ones. The Halliwells did not get that luxury.
- Despite having obtained all of their individual powers, the Charmed Ones were required to accept their destiny as witches in order to access the Power of Three.
- According to Charity Callahan in Exorcise Your Demons, only the Charmed Ones have the Power of Three.
- According to Harry Greenwood in Ambush, as far as anyone knows, there is no Power of Three if one of the Charmed Ones is a demon.
- However, while Macy was the Source (and so, a demon), the sisters could still access the Power of Three.
- Like the original series, the Power of Three is represented on the front cover of the Book of Shadows with the Triquetra symbol.
- Unlike the original, the Charmed Ones were born in every era in times of great need, thus the Power of Three had existed in many sisterhoods. Also unlike the original, carrying the Power of Three had one major consequence: in every generation of Charmed Ones, when the power became too great for them to bear, it would destroy one of the sisters.
- The Power of Three is too much for one being to handle