Spoiler for killing animus
Make sure everybody in your party has resist aether active as he attacks with aether half the time. Use Gloria to lower his spirit, as this will cause his elemental attacks (not aether) to drop to zero damage. Legion can also help if he has pixie dust and you are using him. I used Solaar to heal and he can use aether form in a turn that he doesnt have to heal anybody. The aether attacks from animus will heal Solaar, but will remove him from aether form when he is hit, so watch out. I just used Mardek to slash away at animus, but he can heal as well. I read in some places not to use shields because animus will break them, so I didn't try to use Mardek for that.
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