Contrary to what Osric speculated about Kyran's magic sense, Kyran could only use it offensively within a specific range. After that, he could only use it to observe.
As Kyran said before, he was not omnipotent. If he could attack others by using his magic sense alone, he would have already wiped out Osric's side, just like he did to the enemies inside the Tower of Conclave. It did not matter if Osric was protecting their camp or not. With the Void magic's property, Kyran could destroy or ignore Osric's protection and kill all the mages below Magus with him.
Truth be told, Kyran only managed to kill the enemies inside the Tower of Conclave because they were within the 'specific range' at which he could attack them with his magic sense. Aside from that, they practically invited his magic to finish them off when they used scrolls and tokens that could imitate the Void's warp ability.
