The Trio

The Trio is a name for a group of vampires consisting of, as believed, the three most powerful vampires (vampire weapons) in the world.

The First Trio consisted of: Damian, Emil and Jul. The First Trio was dismissed when Emil and Jul died.

The Second Trio consisted of: Damian, Emilian and Julian. The Second Trio was dismissed when it is revealed Emilian and Julian keep the force of Emil and Jul inside of themselves and that there is someone more powerful than them.

The Third Trio consisted of: Damian, Karolina and Rajan. The Third Trio was dismissed when Rajan was killed by Karolina. After Rajan is killed, the Trio doesn't exist and is renamed in The Duo.

The Duo consisted of: Damian and Karolina. And as Karolina became human, The Duo is dismissed.

Most recently, as Karolina is turned back in the vampire, The Duo is reunited.

Later, when Damian is gone in the finale, the Duo is dismissed for a second time and doesn't exist anymore.

(The Duo actually exists through Irayil, the Last Vampire, and his lover.)