If you need Ability spheres, have a character use the Distill, then summon an Aeon. The game doesn't care how you kill it, just kill it. Summon a replacement if it dies, use an Overdrive if you want. Save spheres are right next to you. Shiva has nice self-heals with Blizzara, but even Valefor should be able to toast one before getting wiped out.