The Saints were a group that was created 1000 years ago in attempt to halt Duo's attempt to take over the world. There are 15 members in all, the leader of the group is Kain Angelo.
They were the protagonist Gathering of the Saints Mini Arc and antagonists in the Saints arc
The group dates back in Guasto during the great war, when Kain Angelo, a leading General and King of the Undian Empire, met Sonorc after a drunk fit left him in Braena Woods.
It was there that Sonorc showed Kain all the terrible things his forces had commited, the mass murder Kain witnessed caused him to revolt against his own Empire and form a group to stop his own creation.
Kain Angelo: The Leader of the Saints, he is a tactician and is incredibly powerful, the only person that Duo saw as his equal. Kain weilds the powers of Odin and Kain's powerful blade, Mani-Katti.