I get to Besaid Temple and they summon Dark Valefor and then its first strike is its overdrive and I can't get the change to do a single thing, not even with Rikku's First Trike! The Energy Ray takes 9999 and they die! How do I defeat it?!

I was stuck there too. And what I do is I put Auot-life on my people. When they died the AL would kick in and they would have life. try that ok

How do I put auto-life on them before the battle begins? Dark Valefor ALWAYS makes the first move with its overdrive!

madhtr do you where i can find a weapon or armour with the auto-life ability?

Skyhigh, you don't 'find' these, you customize them, with Rikku's customization ability.

Firstly, you do know how to use that, yes??

OK, then you have to use that ability on your armour, not weapons, and combine that armour with "mega-pheonix's"..... not sure how many per item though. I think it may be 20. The armour needs to have a slot available to be able to do it.

The weapons are customizable with attacking abilities, and the armour is customizable with defense abilities. Make sense!?!? :P

In order to even comprehend defeating any of the dark aeons, you have to break the HP limit. You can also break the mp and damage limits as well... to do this you need to either aquire everyone's ultimate weapon's and their respective upgrades or just create a weapon that has these attributes. You can, potentially, be able to strike for 99,999 with most characters and have a 99,999 hp gauge and a 9,999 mp gauge... its hard work to attain... if this is still giving you jip, then by a gameshark or an action replay and kick their asses like that... but you'll be a hollow cheater if you do!!! <_<