SPOILERS FOR FUTURE ARC. But if that does not worry you, keep reading.
The highest echelons of the mafia seem to think that a great amount of power could be found in three groups of seven objects:
1. all seven Vongola power rings
2. all seven Mare (pronounced mah-re, like the French word for “sea”) power rings. These are the rings with the oval heads and wings.
3. all seven Arcobaleno pacifiers
This three-of-seven requirement is called the tri-ni-sette.
As of current information, this is how things stand:
– Byakuran has 5 of 7 Arcobaleno pacifiers: sky, thunder, mist, storm, cloud (Several Arcobaleno are dead or missing because of this.)
– Reborn, having been brought from the past, has one Arcobaleno pacifier still with him (yellow, sun)
– Lal Mirch holds the blue (rain) pacifier (hers now from Colonello)
– Byakuran has all 7 Mare rings
– The future version of Tsuna, the actual leader of the Vongola, destroyed the Vongola power rings in his time
– Thus it was necessary to bring in the present-day Vongola guardians, because they still have the Vongola power rings intact
– Because of this, Vongola has all 7 of its power rings
Picture cred: OneManga
Vongola 101 
what about uni’s (the sky) pacifier?
By: dg on August 11, 2009
at 2:25 am
As of current information, Uni still has the Sky pacifier with her. ^^v It’s just that, because of the Millefiore takeover, Byakuran has access to her pacifier too, one of the five he can access.
By: jumpercable on August 11, 2009
at 7:48 am