Here is the next installment of the Life of St. Martin.
It is even agreed that angels were seen by him many times and that, he used to hold conversations with them. Truly, he perceived the devil as so well and kept him under observation that whether the devil retained proper appearance or whether he changed himself into different images of spiritual wickedness, he was seen in any disguise by Martin. (2) When the devil knew that he was not able to escape Martin, he frequently oppressed him with abuse because he was unable to deceive him with trickery. At one times, the devil, holding a bloody horn of a cow, broke into Martin's cell with a great roar. Showing his bloody right hand and rejoicing in the crime which he recently committed, he said "Where is your power, Martin? I killed one of your people just now!" (3) Martin, after calling together the brothers, reported what the devil had told him: he ordered them to go carefully through the cells of each of their brothers since someone had been afflicted by this disaster. They announced that none the monks were missing, but a peasant who was hired by them to bring wood on a wagon, went into the forest. Therefore, Martin ordered them to go to meet him. (4) In this way, the peasant was discovered not far from the monastery almost dead. Drawing his last breath, he told the brothers the cause of his death and wounds. While he was drawing together more tightly the loosened reins on the yoked oxen, one of them, tossing its head, drove its horn into the peasant's groin. Not much later, the man died. You see by what judgement of God, this power is given to the devil. (5) It was remarkable in Martin that not only in this situation which we reported above, but in many of this type that, as often as it happened, Martin foresaw it long before or he told the brothers about the things announced to him.
In this passage, we see a beginning of Sulpicius' evidence of St. Martin's power over the devil himself. Given the generally escalating seriousness of the spiritual threats to Martin, the appearance of St. Martin's contests with the devil makes sense at this point in this Life. One of the striking things about this is the affirmation, at the beginning of this passage, that St. Martin could not be tricked by the devil. That is, he could always discern the devil whatever he did to deceive him. This is an important element of a saint because spiritual discernment is important in spiritual warfare by the saints, so it was important for Sulpicius to emphasize this.
This is followed by an affirmation that the devil was unable to do anything directly to St. Martin himself, but rather was confined to taunting him. This is an expression of St. Martin's spiritual power. This relative immunity from the attacks of the devil is the mark of a saint. Indeed, it is striking as this story unfolds that the devil is unable to injure St. Martin or even his monks. Rather it is someone who is on the fringes of the community, a hired man, whose life in the world, presumably, made him more vulnerable to the assaults of the devil or even irate oxen. The taunts of the devil are a little forced here because, while he achieved a success in injuring someone associated with St. Martin, he did not manage to injure the community itself.
I must say that I was a little surprised that there is no healing element to this story. The poor peasant dies shortly after gasping out his story. While sad for the peasant, a healing wasn't the point of the story. Rather it was St. Martin's foreknowledge of the the devil's designs that Sulpicius highlights. It is clearly suggested that the devil still has power, but that holy men like St. Martin have the gift of foreknowledge and/or discernment to recognize the hand of the devil in the world. That seems to be enough for Sulpicius in this story.