Help me survive against Ermor

Bards can't cast panic. And if it costs you gems, why on earth would you waste them on casting Panic? Just summon masses of Vine Men (No morale issues) if you want to waste gems

Or alternatively get Alteration 4, and have all your bards cast Swarm with as many gems as you can.

OR, use your Sidhe to cast Eagle Eyes and Sleep Cloud (if your problem is only the living Versions)

You can even, if you want, put a Sidhe up front of your army, have him cast Air Shield, and do a "Attack" to get him close then have him sit on "hold, hold hold" so that the Javelins are wasted. Then have your army come in and mop up hand to hand.