Was the Devil Good?

Sexta annotatio indicat eos dicere quod diabolos numquam fuerit bonus, nec natura eius opificium Dei sit, sed eum ex chao et tenebris emersisse: quia scilicet nullum sui habeat auctorem, sed omnis mali ipse sit principium atque substantia: cum fides vera, quae est catholica, omnium creaturarum sive spiritulium, sive corporalium bonam confiteatur substantiam, et mali nullam esse naturam: quia Deus, qui universitatis est conditor, nihil bonum fecit. Unde et diablous bonus esset, si in eo quod factus est permeneat. Sed quia naturali excellentia male usus est, 'et in veritate non stetit', non in contrariam transiit substaniam, sed a summon bono, cui debuit adhaerere, descivit; sicut ipsi qui talia asserunt a veris in falsa proruunt, et naturam in eo arguunt in quo sponte delinquunt, ae pro sua voluntaria perversitate damnantur. Quod utique in ipsis malum erit, et ipsum malum non erit substantia, sed poena substantiae.  Sanctus Leo Magnus, Epistula XV

The sixth note indicates that they say the devil never was good, and that his nature is not God's work, but that he emerged out of chaos and darkness; thus it seems that he has no instigator, but is himself the principle and substance of all evil, yet the true Faith, which is the Catholic, acknowledges that the substance of all creatures spiritual or corporeal is good, and that evil has no existence, because God, who is the Maker of the Universe, made nothing that was not good. Thus even the devil would be good, if he had remained as he was made. But because he made a bad use of his natural excellence, and 'stood not in the truth,'1 he did not pass into the opposite substance, but from the highest good, to which he should have adhered, he revolted: just like those who assert such things and run from the truth into error, accusing nature of their own spontaneous delinquencies, and so they are condemned for their voluntary perversity. Certainly this evil is in them, but is itself not a substance but a penalty substance suffers. Saint Leo the Great, Letter 15 1 Jn 8.44