(OOC: Think! Before he conjured up the Shroud he was cautious, careful, subtle...quite mortal, in other words. But afterwards he was blatant, obvious. He didn't care who knew about the Shroud because he was absolutely positive that he was uncontested. His power only extends as far as the Shroud. Your first priority should be to contain it.
And no, Kayo isn't going to be killed, but because he's a character and I can't kill him without your permission, like Claxtio, not because your word is law. You are not "the GM" of this just because you thought up the basic premise; this is free-form RP. If your villains prove less competent than mine, yours will be killed and mine will survive. If vice versa, mine will die and yours will survive. That's how it works.)
The Shroud receded slightly from Kayo, perhaps ten feet, rearing up tendrils against the invisible barrier of magic created, unable to penetrate it.
The boy, meanwhile, immediately turned his attention to the intruder. He can affect the Shroud with Arcane Magic? That is interesting...I'll have to look into this...and into him. And there's only one easy way to do that. He summoned up several of his minions. Twenty or so in all, they gathered around him. "The boy, at the edge of the Shroud? Bring him inside the Shroud, alive. Bring him to me."
The things shot off to do the will of their master.