There is something special about Auron's arm, there is a reason he doesn't use it...it was a result of something, which was a result of something else. Just wait til later in the game to find out what.
And for the Extractor Boss Fight, I have a strategy.
IT IS NOT WRITTEN BY ME!! IT IS FROM AN FAQ I GOT FROM WWW.GAMEFAQS.COM!!
[BOSS - Extractor]
[4000 HP - 660 AP - Steal Nothing]
Easy, easy. Again, only Wakka and Tidus can fight underwater. Attack it with
everything you have, making sure to use Wakka’s Overdrive correctly. Make sure
you try to get Wakka’s overdrive to get at least 2 thunder elements. Whenever
the Extractor goes above you, have Wakka attack it and Tidus heal. at that
point it is readying depth charges. When they are unleashed, heal up with those
potions you bought. Continue this and the Extractor is gone in no time.
Again....IT IS NOT WRITTEN BY ME!! IT IS FROM AN FAQ I GOT FROM WWW.GAMEFAQS.COM!!
There you go.
And this really belongs in the SE section btw.