V was soul-spliced when she attacked. So in a sense, it's quite reasonable to describe the attackers in the plural. And Jirix knew that.

Clearly the attack has been "spun" to exclude any mention of the phylactery (the last thing Redcloak wants is to make Xykon even angrier than he already is, by publishing that little fiasco to the world), and probably also to make the attack sound bigger and more threatening than it was (to lessen Reddy's own embarrassment at the damage it did). But I don't think Jirix is directly lying, here.

"Unreliable narration" - isn't all narration inherently unreliable? On the other hand, there are places where we see narration that isn't in crayon.

But maybe the crayons are, as Ryuuk said, there to add a more mythic dimension - these are simply things that far transcend the experience of the ordinary listener/viewer.