Ogre Bear is supposed to kill Aire when first encountered. The party can challenge it again in the Animal Burrow once the world is flooded with darkness. Ogre Bear is powerful and the only way to enter the Animal Burrow is to be in animal form with decreased stats.
There are some workarounds to the adverse effects of being in animal form: one is to have someone equip the Beastmastercrown, which negates the stat reduction. Another way to beat it is to have Energy Screens, which grant immunity to physical attacks but have the party take quadruple damage from magic attacks. Ogre Bear only uses melee attacks, but this method isn't recommended as Energy Screens can only be bought as prizes at multiplayer shops, and cost 8,000 points.