Ok in multiplayer mode how am i supposed to get into the planer sphere if it is supposed to be my stronghold? Kill Valygar? Won't that decrease my rep or cause problems later in the game?

Can't you just ask him to meet you there without killing him?

No you either have to kill him or have him in group from what i can figure out. And my char is Good so how do i get in without getting creamed later in the game?

He's an npc killing them doesn't decress rep' and this is his quest, you lose some dialogue with the nercomancer inside the sphere but thats about it. OR you could leave a character outside the sphere pick him up and enter it. then ask him to stay in the sphere and leave and pick up your old character.