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The Arcobaleno is a group made up of the world's strongest seven. The "I Prescelti Sette" ("the chosen seven") of an era are infants that possess Arcobaleno Pacifiers representing the Dying Will Flames of the Sky. Their Pacifiers glow when a member is nearby.
The Arcobaleno members were formerly adults that were cursed into infants in an event known as "The Fated Day". The gathering of strong individuals were brought about by a contracted job or a Representative Battle, for the purpose of harnessing and protecting the power of the Tri-ni-set.
Though each member has the body of an infant, their abilities and intelligence remain intact. But because of their infantile body, their muscle memory and speech were reduced, such as Reborn saying "Ciaossu" rather than "Chaos". In addition to their retained abilities, they can emit Dying Will Flames throughout their entire body. The Arcobaleno are also mentioned to be "walking out of time", meaning that they cannot age or die of old age.
However, the holder of the Sky Arcobaleno Pacifier is an exception. Instead of being cursed with the body of an infant, the holder is cursed with a short lifespan. In Luce's case, she had both curses. The Sky Arcobaleno also has the power of insight, and the power to resurrect deceased Arcobaleno by sacrificing their own life.
Over time, an Arcobaleno may weaken and may be unable to hold the power of the Tri-ni-set. Checker Face, the overseer of the Tri-ni-set, removes the Pacifier, leaving a separate stone Pacifier to the former Arcobaleno. The strain of the removal causes the former Arcobaleno to die or become disabled. Few of those who survived become the Vindice, whose primary goal other than upholding the mafia law is to avenge themselves on Checker Face.
- Luce - the holder of the Sky Pacifier. Her Animal Partner is a squirrel named Cosmo. She is shown to be pregnant with Aria when she was cursed.
- Aria - another holder of the Sky Pacifier. She was the boss of the Giglio Nero Famiglia.
- Yuni - the last holder of the Sky Pacifier. She is the daughter of Aria, and the granddaughter of Luce. Though young, she is the current boss of the Giglio Nero Famiglia.
- Reborn - the holder of the Sun Pacifier and known as the world's strongest hitman. He is Vongola Nono's most trusted member, and Tsuna's home tutor. His Animal Partner is a shape-shifting chameleon named Leon, who usually sits on Reborn's fedora.
- Verde - the holder of the Lightning Pacifier and said to be the smartest Arcobaleno. His Animal Partner is a crocodilian named Keiman.
- Colonnello - the holder of the Rain Pacifier. He is in charge of the training ground behind Mafia Land and was a former member of the COMSUBIN. His Animal Partner is a hawk named Falco.
- Skull - the holder of the Cloud Pacifier and known as the "Immortal Stuntman". He is the head of the combat forces for the Carcassa Famiglia. His animal partner is a giant armored octopus named Oodako whose tentacles follow his hand and finger's movements.
- Viper - the holder of the Mist Pacifier and a powerful spell-caster and illusionist. He is a member of the elite assassination team, Varia, under the name "Esper Mammon". His Animal Partner is a black frog named Fantasma that sits on top of his head.
- Fon - the holder of the Storm Pacifier and is the master of I-Pin. He originates from China and is also an experienced martial artist. His Animal Partner is a monkey, most likely a bald uakari, named Lichi, who sits atop his head.
- Lal Mirch - the holder of a corrupted Pacifier, due to Colonnello's intervention. She was still inflicted partially with the Arcobaleno Curse. Her curse was not solidified, and as such, she, unlike the other Arcobaleno, is prone to aging over time. She works alongside Iemitsu Sawada in CEDEF.
- Bermuda von Veckenschtein - a former Arcobaleno who is now a member of the Vindice. He is a holder of the Clear Pacifier, the pacifier of the Flame of Night, which was shown to be in Checker Face's possession later on when he gathered the current generation of Arcobaleno.
- Interestingly, while Arcobaleno is the Italian word for "rainbow" and arco is an Italian word for "bow or arc", baleno actually translates to lightning.
- There are 10 known Pacifiers, but only 7 spaces on the 7³ (Tri-Ni-Set).
- The color of a Pacifier is the same color as the owner's Flame.
- Interestingly, the Arcobaleno have personalities that are opposite that of their respective flames' roles, whereas the Vongola have personalities that match their respective flames' roles.
- All of the previous and current Sky Arcobaleno have an orange clover mark below the left eye around the cheek, which was later determined as the embed logo of Giglio Nero Famiglia.
- All of the Arcobaleno, except for Lal Mirch, Aria, and Yuni have an animal partner.
- In the opening Listen to the Stereo, Lal Mirch has a blue spotlight because she was supposed to be the Rain Arcobaleno.