Ceifeed and Shabranigdu fought for dominance from the moment of their creation. In their last battle, which occured roughly around 4000 BK(?) and is known as the Shinma War, Ceifeed theoretically used up his power completely when creating his four subordinates and cutting Ruby Eye into seven pieces, and it is believed that he sank into the Sea of Chaos, forever disappearing from the world.
Still, it seems that some amount of Ceifeed's power did remain, as from generation to generation, humans known as Knights of Ceifeed appear, who posses enormous power thanks to the fragment of the Flare Dragon within them (although the exact nature of this power is unknown). The only currently known knight is Luna Inverse.
Ceifeed is worshipped by numerous humans, especially in Saillune. Because of this some suspect that his remaining power might be behind the mysterious origins of white magic, although official sources say otherwise.