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Viper is an Arcobaleno that holds the Mist Arcobaleno Pacifier. He is working for the Varia, the independent assassination squad of the Vongola Famiglia, under his chosen name Esper Mammon. Known as the Varia's best spell caster, Viper has the ability to cast illusions as well as being able to locate any person by sneezing into a piece of paper.
Both as an adult and in Arcobaleno form, Viper is shown wearing a black outfit with a hood that covers his eyes, making it hard to know his gender. Before becoming an Arcobaleno, Viper is seen to have chin-length purple-colored hair and fairly white skin. He has two triangular purple markings on his cheek that extend to his jawline when he use their Arcobaleno powers. In his Arcobaleno form, his mouth is shaped like an upside-down V.
He also have a dark green frog named Fantasma that lies on top of his head. His Arcobaleno Pacifier is covered with the Mammon Chain, preventing other Arcobaleno to sense him while also preventing the use of his powers. The chain is replaced by the Vongola by the cap that conceals the Rings' powers the same way as the Chains.
As an Arcobaleno, they carry with him a roll of what seems to be tissue and uses it to create illusions to attack his opponents.
As the representative of Greed, Viper only works when money is involved, with the exception of the Arcobaleno Trials. He is materialistic, and is generally apathetic, though he showed more emotion when they were trying to break the Arcobaleno curse, and vehemently expressed his desire to continue living. He tends to charge very high prices for his services.
Weapons and Abilities
Before he was turned into an Arcobaleno, he was a first-class psychic who added Illusions to his repertoire. It was seen he could also fly before he was turned into an Arcobaleno. His psychic ability was telepathy, and he could also dowse things through pieces of paper so that he could find objects and people. As an Arcobaleno he still has all of his powers, but his Illusions have been strengthened, possibly because the Arcobaleno Mist Pacifer is an object of the Tri-ni-set that emits Mist Flames, creating real Illusions, and giving the wielder the Arcobaleno's ability to emit Dying Will Flames from their bodies.
- Illusions: As the Mist Arcobaleno, his Illusions is first class; the only time he was defeated by another Illusionist was when he fought Mukuro during the Mist Ring Battle. His most commonly seen used Illusions are Illusions of clones of themselves and the Illusion of tentacles.
- Viper Mirage: One of Viper's many Illusion abilities; he used this to surround Namimori with a series of mirages.
- Viper Mirage R: One of Viper's illusions that sets a rule on the target of which the illusion is cast on. If the rule is broken by the target, the target is instantly damaged with a multitude of deep cuts.
- Thoughtography: The ability to locate any person by sneezing into a piece of paper; the spit or mucus that sticks to the paper shows a map leading to the desired person.
- Flight: Viper can fly because of his Animal Partner Fantasma's abilities, but he has been shown to be able to fly without Fantasma's assistance.
- Uroboros: Declared by Viper himself to be his strongest illusion, Viper unleashes multiple large blind eel-like creatures with large mouths and sharp teeth.
- Mist Starfish: It was one of the first Box Weapons that were created and appeared in the past. It was used by Viper against Yamamoto and Ryohei during the 3rd Trial. When used, many spinning Starfish that emit Mist-Flames come out of it. Those that break are fused together and create a single and bigger Starfish.
- The word "Mammon" is a term used to describe material wealth or greed, most often personified as a deity.
- He dislikes being called by his given name, Viper.
- The name Viper refers to a type of snake, reflecting his choice of animal partner.
- His favorite word is 'greed', reflecting his own name.
- His favorite food is 5-yen chocolate, while his favorite drink is lemonade.
- His hobby is checking his deposit amount.
- He dislikes leaving his debts unpaid.
- Viper's gender has been a debate among fans due to the use of gender-neutral pronouns used to describe them. He was grouped into the male character category in the third popularity poll, and his gender continues to remain as male in the official VIZ translations, though VIZ itself is not "official" and has become infamous for making many errors and not adhering to the original text when translating.
- Viper has a character song: Maboroshi no Arcobaleno.
- In the official English translation, Reborn and Colonnello said that his Arcobaleno Pacifier had a "sunny glow."
- In Drama CD: Namimori Radio, it was revealed that he and Belphegor once borrowed one of Leviathan's parabolas when the weather was rainy, but ended up being struck by lightning.
- In Haru's Haru Haru Interview: Dangerous, it's revealed that like Fon, he cannot eat Mapo Tofu since he turned into a baby because it was spicy, which makes him choke and tear up.
- Viper only likes to work if he gets paid. On rare occasions, Viper works for free only if the situation is dire or out of his duties as an Arcobaleno.
- Viper and Belphegor appear to be very close, as Viper avoids most of the Varia members and is mainly seen with Belphegor.