Dardanides contra furit: Anxuris ense sinistram
et totum clipei ferro deiecerat orbem (545-6)
So, all the MSS read ferro, but Harrison says ferro and ense can't both refer to his sword here. He reads terrae, which he thinks provides a nice contrast with caelo below (and isn't too in conflict with deturbat terrae, since that's 10 lines later). Also, some people conjecture ecce for ense, but apparently Virgil never uses ecce with a pluperfect.
While not exactly the same situation, I remembered this bit earlier:
proxima quaeque metit gladio latumque per agmen
ardens limitem agit ferro (513-4)
Granted, there are two separate verbs, but both ablatives are referring to Aeneas' sword.
Though I'm not at all against reading terrae, tbh.