*Source: link (i don't own this,just borrow it:D)
Much is speculated about the seven Arcobaleno. There are seven. या depending on how well informed the person you're talking to, there are eight, या seven and a half of them. Three are rumored to have allied themselves with the Vongola family. One is unable to die. Another is the master of all things perceived. One is the smartest man on the planet. Another is the ultimate assassin. One is the strongest martial artist ever seen. Such are the rumors about the Arcobaleno.

But for all the rumors and speculation, you'll be hard pressed to ever come...