I'd be inclined to say, spend a season developping Demon's eternal oblivion with an unstandard target like Room. Remind your new guests that, even if they somehow can slip through your Aegis, they still suffer the negative effect of the aura to their Magic Resistance while you gain the bonus to spellcasting. If the covenant aura is already dominated by an infernal aura... screw it and move on, or fortify a small part of the covenant under magic aura with a new aegis cast on a non-standard date, and use that location as the base from which to fight from.