He watched as his parents, friends, and even his wife Lois died without the ability to save them from natural causes. Continuing his service as the world's foremost champion, Superman began to slow as the sadness of the losses grew. Legend then tells how close to the end of the twenty first century, Superman Prime (as history will remember as Kal-El) passed the responsibilities of being Superman to his heir, Superman Secundus, and created the Superman Dynasty. Then, one day, he left Earth.
Superman's travels lasted from the 21st Century to the turn of the 700th Century. During this 679 century odyssey, he acquired vast abilities and skills from every being he met and gained perfection over all the abilities he received. He even broke through the Source Wall and studied under the Source itself, meaning he could have a portion of the Source's power or more. The true extent of abilities he received from the Source are unknown. When he returned to Earth, he forged a covenant with his descendants. In this conenant, he would bestow upon them a small fraction of his power as long as they served for truth and justice. He also gained the abilities of his lineage and magnified them with his own power (for example, the Superman of the 67th century married the queen of the 5th Dimension, GZNTPLZK, which in turn gave Superman Prime the abilities and powers of a 5th Dimension Imp). After the covenant he left and returned to his Fortress of Solitude in the center of the Super Sun. (DC One Million)
He heard of a fake god naming himself Ku Vu Kin and wants to see for himself that he strong as he thinks he is, so superman will battle him.