Mage stronghold quest?

So, I know that Valygar and the sphere quest have something to do with getting the mage stronghold. Is it best to do the sphere quest or to just turn him into the council building to Tolgerias? And if I have to do the sphere quest I guess that means I have to take Valygar into my party? Who do I drop in order to fit him into the group? Either Keldorn (haven't done unseeing eye quest yet), Minsc, or J what's his name thief you get in the beginning of the game? Any help here would be great! Thanks!

P.S. I would then drop Valygar after finishing the sphere, so I don't want to drop someone I will have a hard time re-recruiting.

this might be a spoiler
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if you have his body you[i read this in an earlier thread]you can still get in the sphere and if you a mage you get the sphere as your stronghold