Mid Game+ magic.

[sushiboat]

If you lost a SC to Ermor AE, it's because relying on life drain items is a big mistake. (I thought you said in your first post that you had handled Ermor easily and were floudering after defeating Ermor.) You can't life drain from lifeless units, such as most AE undead. Most undead are also resistant to cold, so an Ice Devil isn't the best match (though it should do fine with the right equipment). Herald Lance and Charcoal Shield are good, or you can go with the double-handed Flambeau.

You shouldn't rely on a single set of equipment for a SC. You have to know the best equipment for the situation.