Beat seporioth? Its not so hard i did beat him and i was only lvl 65, and i did beat him without knights of the round teable, i used clouds last limit, omnislash, (omnislash kan by get by getting 32000 battlepoints or higher in the battle arena in gold souccer) or you ll have to train to lvl 70 or higher to beat him, i now play with my team i always use barret tiva and cloud thay are sure strong on lvl 79 (its the 2 nd time i ll play ff VII
BYE
I am confused, if you beat Emerald Weapon and have the Earth Harp did you trade it to the Kalm Traveler for the three master materia? If you do that you GET Knights of the Round that easy.
As for Ruby Weapon, the BEST strategy to beat him is go in with 2 party members already 0HP so he will dig he claws into the ground. Once you do that you can damage him.
If you missed Bahamut Zero you should be able to dig him up at the Bone Village but I can't remember where at, there are a lot of Materia buried there. Be warned though if you DO have Knights of the Round and your characters level 99, Sephiroth will be really disappointing.